All-solid state secondary battery, particles for all-solid state secondary battery, solid electrolyte composition for all-solid state secondary battery, and electrode sheet for all-solid state secondary battery, and methods for manufacturing same

ABSTRACT

Provided are an all-solid state secondary battery including inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more, particles for an all-solid state secondary battery, a solid electrolyte composition for an all-solid state secondary battery for which the particles are used, an electrode sheet for an all-solid state secondary battery, and an all-solid state secondary battery, and methods for manufacturing the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No. PCT/JP2016/088574 filed on Dec. 22, 2016, which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2015-255356 filed in Japan on Dec. 25, 2015. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an all-solid state secondary battery, particles for an all-solid state secondary battery, a solid electrolyte composition for an all-solid state secondary battery, and an electrode sheet for an all-solid state secondary battery, and methods for manufacturing the same.

2. Description of the Related Art

For lithium ion batteries, electrolytic solutions have been used. Attempts are underway to produce all-solid state secondary batteries in which all constituent materials are solid by replacing the electrolytic solutions with solid electrolytes. Reliability in terms of all performance of batteries is an advantage of techniques of using inorganic solid electrolytes. For example, to electrolytic solutions being used for lithium ion secondary batteries, flammable materials such as carbonate-based solvents are applied as media. In lithium ion secondary batteries, a variety of safety measures are employed. However, there is a concern that disadvantages may be caused during overcharging and the like, and there is a demand for additional efforts. All-solid state secondary batteries in which a solid electrolyte is used are considered as a fundamental solution therefor.

Another advantage of all-solid state secondary batteries is the suitability for increasing energy density by means of the stacking of electrodes. Specifically, it is possible to produce batteries having a structure in which electrodes and electrolytes are directly arranged in series. At this time, metal packages sealing battery cells and copper wires or bus-bars connecting battery cells may not be provided, and thus the energy density of batteries is significantly increased. In addition, favorable compatibility with positive electrode materials capable of increasing potentials and the like can also be considered as advantages.

Due to the respective advantages described above, all-solid state secondary batteries are being developed as next-generation lithium ion batteries. For example, JP2014-112485A describes a solid battery containing a hydrocarbon-based polymer having a crosslinking structure in any one of a positive electrode, a negative electrode, and an electrolyte layer including a sulfide-based solid electrolyte. In addition, JP2001-15153A describes an all-solid state secondary battery in which a plurality of battery elements provided by sequentially laminating a positive electrode made of an inorganic compound, a solid electrolyte, and a negative electrode is disposed on a collector, and the plurality of battery elements is disposed with gaps of 0.1 to 5,000 μm.

SUMMARY OF THE INVENTION

The invention described in JP2014-112485A intends to prevent the generation of dendrites and improve the cycle characteristic using the hydrocarbon-based polymer having a crosslinking structure while preventing the degradation of adhesiveness between the electrode layer and the solid electrolyte layer. However, in the solid battery described in the same document, the bonding property between solid particles of the solid electrolyte and the like is poor, and this poor bonding property causes poor handleability during the production of the solid battery. Meanwhile, in the all-solid state secondary battery described in JP2001-15153A as well, similarly, the bonding property between solid particles is poor.

Therefore, an object of the present invention is to provide an all-solid state secondary battery having an excellent bonding property between solid particles in individual layers, between individual layers, and between a layer and a collector. In addition, another object of the present invention is to provide particles for an all-solid state secondary battery having an excellent bonding property. Furthermore, still another object of the present invention is to provide a solid electrolyte composition for an all-solid state secondary battery, an electrode sheet for an all-solid state secondary battery, and an all-solid state secondary battery for which the particles for an all-solid state secondary battery are used and methods for manufacturing the same.

As a result of intensive studies, the present inventors found that, in a case in which at least one kind of solid particles that are included in an all-solid state secondary battery such as an electrode active material or an inorganic solid electrolyte are exposed to actinic rays, thereby producing functional groups (hydrophilization) so as to obtain a proportion of a nitrogen element in the element composition of a solid particle surface in a specific range, affinity between the solid particles improves, and the bonding property between solid particles in individual layers of the all-solid state secondary battery, between individual layers, and between a layer and a collector improves. The present invention has been made on the basis of this finding.

That is, the object is achieved by the following means.

<1> An all-solid state secondary battery comprising: inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more.

<2> The all-solid state secondary battery according to <1>, further comprising: auxiliary conductive agent particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.

<3> The all-solid state secondary battery according to <1> or <2>, in which the proportion of the nitrogen element in the element composition of the particle surface is set to 0.1 atm % or more by an actinic ray.

<4> The all-solid state secondary battery according to any one of <1> to <3>, in which the inorganic solid electrolyte particles are oxide-based or sulfide-based inorganic solid electrolyte particles.

<5> The all-solid state secondary battery according to any one of <1> to <4>, in which the electrode active material particles are selected from the group consisting of electrode active material particles represented by any one of Formulae (B1) to (B5) and electrode active material particles belonging to (B6),

Li_(a1)M¹O_(b1)  Formula (B1)

Li_(c1)M² _(m1)O_(d1)  Formula (B2)

Li_(e1)M³ _(m2)(PO₄)_(f1)  Formula (B3)

Li_(g1)M⁴(PO₄)_(h1)X_(i1)  Formula (B4)

Li_(j1)M⁵(SiO₄)_(k1)  Formula (B5)

(B6) a carbonaceous material, tin, silicon, indium, and oxides and sulfides thereof

In Formula (B1), M¹ represents a metal including at least one of Co, Ni, Fe, Mn, Cu, or V, a1 represents 0 to 1.2, and b1 represents 1 to 3.

In Formula (B2), m1 represents an integer of 2 to 8, a plurality of M²'s each independently represents a metal including at least one of Co, Ni, Fe, Mn, Cu, Cr, or V, c1 represents 0 to 2, and d1 represents 3 to 8.

In Formula (B3), M³ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, m2 represents an integer of 1 to 8, e1 represents 0.1 to 3, and f1 represents 1 to 5. In a case in which a plurality of M³'s is present, the plurality of M³'s may be identical to or different from each other.

In Formula (B4), M⁴ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, X represents a halogen atom, g1 represents 0.1 to 3, h1 represents 1 to 5, and i1 represents 0.1 to 5.

In Formula (B5), M⁵ represents a metal including at least one of Co, Fe, Mn, Ni, Cu, or V, j1 represents 0 to 3, and k1 represents 1 to 5.

<6> The all-solid state secondary battery according to any one of <1> to <5>, in which the proportion of the nitrogen element in the element composition of the surface of at least one kind of the particles is 0.1 atm % or more, and one or more Raman spectral spectrum peaks are detected in at least one range of

3,200 cm⁻¹ to 3,800 cm⁻¹,

2,000 cm⁻¹ to 2,280 cm⁻¹,

1,500 cm⁻¹ to 1,800 cm⁻¹, or

1,020 cm⁻¹ to 1,250 cm⁻¹.

<7> The all-solid state secondary battery according to any one of <1> to <6>, further comprising: a binder.

<8> The all-solid state secondary battery according to <7>, in which the binder has an acidic group.

<9> A method for manufacturing the all-solid state secondary battery according to any one of <1> to <8>, comprising: a step of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by an actinic ray.

<10> The method for manufacturing the all-solid state secondary battery according to <9>, in which the actinic ray is plasma generated from a gas of any one of nitrogen, oxygen, hydrogen, carbon dioxide, ammonia, helium, and argon or a gas mixture of two or more thereof.

<11> The method for manufacturing the all-solid state secondary battery according to <10>, in which the plasma is low-temperature atmospheric pressure plasma.

<12> Particles for an all-solid state secondary battery which are electrode active material particles selected from the group consisting of inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table, auxiliary conductive agent particles or electrode active material particles represented by any one of Formulae (B1) to (B5), and electrode active material particles belonging to (B6), in which a proportion of a nitrogen element in an element composition of a particle surface is 0.1 atm % or more.

Li_(a1)M¹O_(b1)  Formula (B1)

Li_(c1)M² _(m1)O_(d1)  Formula (B2)

Li_(e1)M³ _(m2)(PO₄)_(f1)  Formula (B3)

Li_(g1)M⁴(PO₄)_(h1)X_(i1)  Formula (B4)

Li_(j1)M⁵(SiO₄)_(k1)  Formula (B5)

(B6) a carbonaceous material, tin, silicon, indium, and oxides and sulfides thereof

In Formula (B1), M¹ represents a metal including at least one of Co, Ni, Fe, Mn, Cu, or V, a1 represents 0 to 1.2, and b1 represents 1 to 3.

In Formula (B2), m1 represents an integer of 2 to 8, a plurality of M²'s each independently represents a metal including at least one of Co, Ni, Fe, Mn, Cu, Cr, or V, c1 represents 0 to 2, and d1 represents 3 to 8.

In Formula (B3), M³ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, m2 represents an integer of 1 to 8, e1 represents 0.1 to 3, and f1 represents 1 to 5.

In a case in which a plurality of M³'s is present, the plurality of M³'s may be identical to or different from each other.

In Formula (B4), M⁴ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, X represents a halogen atom, g1 represents 0.1 to 3, h1 represents 1 to 5, and i1 represents 0.1 to 5.

In Formula (B5), M⁵ represents a metal including at least one of Co, Fe, Mn, Ni, Cu, or V, j1 represents 0 to 3, and k1 represents 1 to 5.

<13> A method for manufacturing the particles for an all-solid state secondary battery according to <12>, comprising: a step of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by an actinic ray.

<14> A solid electrolyte composition for an all-solid state secondary battery which is used for the all-solid state secondary battery according to any one of <1> to <8>, the solid electrolyte composition comprising: inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more.

<15> The solid electrolyte composition for an all-solid state secondary battery according to <14>, further comprising: auxiliary conductive agent particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.

<16> A method for manufacturing the solid electrolyte composition for an all-solid state secondary battery according to <14> or <15>, comprising: a step of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by an actinic ray.

<17> An electrode sheet for an all-solid state secondary battery which is used for the all-solid state secondary battery according to any one of <1> to <8>, the electrode sheet comprising: inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more.

<18> The electrode sheet for an all-solid state secondary battery according to <17>, further comprising: auxiliary conductive agent particles, in which a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.

<19> A method for manufacturing the electrode sheet for an all-solid state secondary battery according to <17>, comprising: Steps [1] and [2] below in this order.

Step [1] of applying a solid electrolyte composition containing inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table and electrode active material particles.

Step [2] of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by irradiating the solid electrolyte composition with an actinic ray.

<20> A method for manufacturing the electrode sheet for an all-solid state secondary battery according to <18>, comprising: Steps [1] and [2] below in this order.

Step [1] of applying a solid electrolyte composition containing inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table, electrode active material particles, and auxiliary conductive agent particles.

Step [2] of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by irradiating the solid electrolyte composition with an actinic ray.

In the description of the present invention, numerical ranges expressed using “to” include numerical values before and after “to” as the lower limit value and the upper limit value.

In the description of the present invention, “acryl” or “(meth)acryl” is used to refer to both methacryl and acryl.

In the description of the present invention, the proportion of the nitrogen element in the element composition of the particle surface refers to a value computed by X-ray photoelectron spectroscopy (XPS (trade name: PHI 5000 VersaProbe II, ULVAC-PHI, Incorporated)).

A photoelectron spectrum that is obtained by photoelectron spectroscopy shows the bond energy value (eV) of a measurement electron to the atomic nucleus in the horizontal axis and the intensity of an emitted photoelectron in the vertical axis. The bond energy value is a value that is dependent on an element, the electron state, and the like and thus enables the compositional analyses of materials. A quantitative value is obtained by computing the area intensity of each peak intensity.

The proportion of the nitrogen atom is computed from a peak that is detected at 396.2 eV to 408.2 eV which is the bond energy value of the is electron orbit to the atomic nucleus.

The all-solid state secondary battery of the present invention is excellent in terms of the bonding property between solid particles in the individual layers, between the individual layers, and between the layer and the collector. The particles for an all-solid state secondary battery of the present invention are excellent in terms of the bonding property. In addition, the solid electrolyte composition for an all-solid state secondary battery of the present invention is capable of enhancing the bonding property between solid particles in individual layers of an all-solid state secondary battery, between the individual layers, and between the layer and a collector by being used to produce the all-solid state secondary battery. In addition, the electrode sheet for an all-solid state secondary battery of the present invention is capable of enhancing the bonding property between solid particles in individual layers of an all-solid state secondary battery, between the individual layers, and between the layer and a collector by being used in the all-solid state secondary battery. Furthermore, the methods for manufacturing the all-solid state secondary battery, the particles for an all-solid state secondary battery, the solid electrolyte composition for an all-solid state secondary battery, and the electrode sheet for an all-solid state secondary battery of the present invention can be preferably used to manufacture the all-solid state secondary battery, the particles for an all-solid state secondary battery, the solid electrolyte composition for an all-solid state secondary battery, and the electrode sheet for an all-solid state secondary battery.

The above-described and other characteristics and advantages of the present invention will be further clarified by the following description with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a vertical cross-sectional view schematically illustrating an all-solid state secondary battery according to a preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred Embodiment

FIG. 1 is a cross-sectional view schematically illustrating an all-solid state secondary battery (lithium ion secondary battery) according to a preferred embodiment of the present invention. In the case of being seen from the negative electrode side, an all-solid state secondary battery 10 of the present embodiment has a negative electrode collector 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode collector 5 in this order. The respective layers are in contact with one another and have a laminated structure. In a case in which the above-described structure is employed, during charging, electrons (e⁻) are supplied to the negative electrode side, and lithium ions (Li⁺) are accumulated on the negative electrode side.

On the other hand, during discharging, the lithium ions (Li⁺) accumulated on the negative electrode side return to the positive electrode, and electrons are supplied to an operation portion 6. In the example illustrated in the drawing, an electric bulb is employed as the operation portion 6 and is lit by discharging. A solid electrolyte composition for an all-solid state secondary battery of the present invention can be preferably used as a material forming the negative electrode active material layer, the positive electrode active material layer, and the solid electrolyte layer.

The thicknesses of the positive electrode active material layer 4, the solid electrolyte layer 3, and the negative electrode active material layer 2 are not particularly limited. Meanwhile, in a case in which the dimensions of ordinary batteries are taken into account, the thicknesses are preferably 10 to 1,000 μm and more preferably 20 μm or more and less than 500 μm. In the all-solid state secondary battery of the present invention, the thickness of at least one layer of the positive electrode active material layer 4, the solid electrolyte layer 3, or the negative electrode active material layer 2 is still more preferably 50 μm or more and less than 500 μm.

In the present specification, there are cases in which the positive electrode active material layer and the negative electrode active material layer are collectively referred to as electrode layers. In addition, as electrode active materials that can be used in the present invention, there are a positive electrode active material that is included in the positive electrode active material layer and a negative electrode active material that is included in the negative electrode active material layer, and there are cases in which either or both layers are simply referred to as active materials or electrode active materials.

Hereinafter, a solid electrolyte composition for an all-solid state secondary battery of the present invention which can be preferably used to manufacture an all-solid state secondary battery of the present invention will be described.

<Solid Electrolyte Composition for all-Solid State Secondary Battery>

A solid electrolyte composition for an all-solid state secondary battery of the present invention includes inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table and electrode active material particles. In addition, the solid electrolyte composition for an all-solid state secondary battery of the present invention preferably includes auxiliary conductive agent particles.

Here, in the solid electrolyte composition for an all-solid state secondary battery of the present invention, the proportion of a nitrogen element in the element composition of the surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm %. In addition, in a case in which the solid electrolyte composition for an all-solid state secondary battery of the present invention includes auxiliary conductive agent particles, the proportion of a nitrogen element in the element composition of the surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.

Hereinafter, inorganic solid electrolyte particles in which the proportion of a nitrogen element in the element composition of the surface is 0.1 atm % or more, electrode active material particles in which the proportion of a nitrogen element in the element composition of the surface is 0.1 atm % or more, and auxiliary conductive agent particles in which the proportion of a nitrogen element in the element composition of the surface is 0.1 atm % or more will be referred to as the particles for an all-solid state secondary battery of the present invention.

Meanwhile, hereinafter, there are also cases in which inorganic solid electrolyte particles will be referred to as an inorganic solid electrolyte, electrode active material particles will be referred to as an electrode active material, and auxiliary conductive agent particles will be referred to as an auxiliary conductive agent.

(Inorganic Solid Electrolyte)

The inorganic solid electrolyte is an inorganic solid electrolyte, and the solid electrolyte refers to a solid capable of migrating ions therein.

The inorganic solid electrolyte is clearly differentiated from organic solid electrolytes (polymer electrolytes represented by polyethylene oxide (PEO) or the like and organic electrolyte salts represented by lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) since the inorganic solid electrolyte does not include any organic substances, that is, a carbon atom. In addition, the inorganic solid electrolyte is a solid in a static state, and thus cations and anions are not disassociated or liberated, and the inorganic solid electrolyte is also clearly differentiated from inorganic electrolyte salts in which cations and anions are disassociated or liberated in electrolytic solutions or polymers (LiPF₆, LiBF₄, lithium bis(fluorosulfonyl)imide (LiFSI), LiCl, and the like). The inorganic solid electrolyte is not particularly limited as long as the inorganic solid electrolyte has conductivity for ions of metal elements belonging to Group I or II of the periodic table and is generally a substance not having electron conductivity.

In the present invention, the inorganic solid electrolyte is added to the solid electrolyte composition for an all-solid state secondary battery. Particularly, an inorganic solid electrolyte having conductivity for ions of metal elements belonging to Group I or II of the periodic table is preferably added thereto. As the inorganic solid electrolyte, it is possible to appropriately select and use solid electrolyte materials that are ordinarily used for this kind of products. Typical examples of the inorganic solid electrolyte include (i) sulfide-based inorganic solid electrolytes and (ii) oxide-based inorganic solid electrolytes.

(i) Sulfide-Based Inorganic Solid Electrolytes

Sulfide inorganic solid electrolytes are not particularly limited as long as the sulfide inorganic solid electrolytes contain sulfur atoms (S), have ion conductivity for metal elements belonging to Group I or II of the periodic table, and have an electron-insulating property. The sulfide inorganic solid electrolyte is, for example, a lithium ion-conductive inorganic solid electrolyte satisfying a composition represented by Formula (1).

Li_(a)M_(b)P_(c)S_(d)A_(e)  (1)

In Formula (1), M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al, and Ge. Among these, B, Sn, Si, Al, and Ge are preferred, and Sn, Al, and Ge are more preferred. A represents I, Br, Cl, and F and is preferably I or Br and particularly preferably I. a to e represent the compositional ratios among the respective elements, and a:b:c:d:e preferably satisfies 1 to 12:0 to 1:1:2 to 12:0 to 5. Furthermore, a is preferably 1 to 9 and more preferably 1.5 to 4. Furthermore, b is preferably 0 to 0.5. Furthermore, d is preferably 3 to 7 and more preferably 3.25 to 4.5. Furthermore, e is preferably 0 to 3 and more preferably 0 to 2.

In Formula (1), the compositional ratios among Li, M, P, and S are preferably b=0 and e=0, more preferably b=0, e=0, and the ratio among a, c, and d (a:b:c) is 1 to 9:1:3 to 7, and still more preferably b=0, e=0, and a:c:d=1.5 to 4:1:3.25 to 4.5.

The compositional ratios among the respective elements can be controlled by adjusting the amounts of raw material compounds blended to manufacture the sulfide-based inorganic solid electrolyte as described below.

The sulfide-based inorganic solid electrolytes may be non-crystalline (glass) or crystallized (made into glass ceramic) or may be only partially crystallized.

The ratio between Li₂S and P₂S₅ in Li—P—S-based glass and Li—P—S-based glass ceramic is preferably 65:35 to 85:15 and more preferably 68:32 to 75:25 in terms of the molar ratio between Li₂S:P₂S₅. In a case in which the ratio between Li₂S and P₂S₅ is set in the above-described range, it is possible to increase the lithium ion conductivity. Specifically, the lithium ion conductivity can be preferably set to 1×10⁻⁴ S/cm or more and more preferably set to 1×10⁻³ S/cm or more. The upper limit is not particularly limited, but realistically 1×10⁻¹ S/cm or less.

In the present invention, Li—P—S-based glass is preferably used.

Specific examples of compounds of the sulfide-based inorganic solid electrolytes include compounds formed using a raw material composition containing, for example, Li₂S and a sulfide of an element of Groups XIII to XV. More specific examples thereof include Li₂S—P₂S₅, Li₂S—LiI—P₂S₅, Li₂S—LiI—Li₂O—P₂S₅, Li₂S—LiBr—P₂S₅, Li₂S—Li₂O—P₂S₅, Li₂S—Li₃PO₄—P₂S₅, Li₂S—P₂S—P₂O₅, Li₂S—P₂S₅—SiS₂, Li₂S—P₂S₅—SnS, Li₂S—P₂S₅—Al₂S₃, Li₂S—GeS₂, Li₂S—GeS₂—ZnS, Li₂S—Ga₂S₃, Li₂S—GeS₂—Ga₂S₃, Li₂S—GeS₂—P₂S₅, Li₂S—GeS₂—Sb₂S₅, Li₂S—GeS₂—Al₂S₃, Li₂S—SiS₂, Li₂S—Al₂S₃, Li₂S—SiS₂—Al₂S₃, Li₂S—SiS₂—P₂S₅, Li₂S—SiS₂—P₂S₅—LiI, Li₂S—SiS₂—LiI, Li₂S—SiS₂—Li₄SiO₄, Li₂S—SiS₂—Li₃PO₄, Li₁₀GeP₂S₁₂, and the like. Among these, crystalline and/or amorphous raw material compositions consisting of Li₂S—P₂S₅, Li₂S—GeS₂—Ga₂S₃, Li₂S—LiI—P₂S₅, Li₂S—LiI—Li₂O—P₂S₅, Li₂S—GeS₂—P₂S₅, Li₂S—SiS₂—P₂S₅, Li₂S—SiS₂—Li₄SiO₄, Li₂S—SiS₂—Li₃PO₄, Li₂S—Li₃PO₄—P₂S₅, Li₂S—GeS₂—P₂S₅, and Li₁₀GeP₂S₁₂ are preferred due to their high lithium ion conductivity. Examples of a method for synthesizing sulfide-based inorganic solid electrolyte materials using the above-described raw material compositions include an amorphorization method. Examples of the amorphorization method include a mechanical milling method and a melting quenching method. Among these, the mechanical milling method is preferred. This is because treatments at normal temperature become possible, and it is possible to simplify manufacturing steps.

(ii) Oxide-Based Inorganic Solid Electrolytes

Oxide-based inorganic solid electrolytes are not particularly limited as long as the oxide-based inorganic solid electrolytes contain oxygen atoms (O), have an ion conductivity of metals belonging to Group I or II of the periodic table, and have electron-insulating properties.

The ion conductivity of the lithium ion-conductive oxide-based inorganic solid electrolyte is preferably 1×10⁻⁶ S/cm or more, more preferably 5×10⁻⁶ S/cm or more, and particularly preferably 1×10⁻⁵ S/cm or more. The upper limit is not particularly present and realistically 1×10⁻² S/cm or less.

Specific examples of the compounds include Li_(xa)La_(ya)TiO₃ [xa satisfies 0.3≤xa≤0.7 and ya satisfies 0.3≤ya≤0.7] (LLT); Li_(xb)La_(yb)Zr_(zb)M^(bb) _(mb)O_(nb) (M^(bb) is one or more elements selected from the group consisting of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In and Sn, xb satisfies 5≤xb≤10, yb satisfies 1≤yb≤4, zb satisfies 1≤zb≤4, mb satisfies 0≤zb≤2, and nb satisfies 5≤nb≤20.); Li_(xc)B_(yc)M^(cc) _(zc)O_(nc) (in the formula, M^(cc) is one or more elements selected from the group consisting of C, S, Al, Si, Ga, Ge, In, and Sn, xc satisfies 0≤xc≤5, yc satisfies 0≤yc≤1, zc satisfies 0≤zc≤1, and nc satisfies 0≤nc≤6); Li_(xd)(Al, Ga)_(yd)(Ti, Ge)_(zd)Si_(ad)P_(md)O_(nd) (here, xd satisfies 1≤xd≤3, yd satisfies 0≤yd≤1, zd satisfies 0≤zd≤2, ad satisfies 0≤ad≤1, md satisfies 1≤md≤7, and nd satisfies 3≤nd≤13); Li_((3-2xe))M^(ee) _(xe)D^(ee)O (xe represents a number of 0 or more and 0.1 or less, and M^(ee) represents a divalent metal atom. D^(ee) represents a halogen atom or a combination of two or more halogen atoms.); Li_(xf)Si_(yf)O_(zf) (xf satisfies 1≤xf≤5, yf satisfies 0≤yf≤3, and zf satisfies 1≤zf≤10); Li_(xg)S_(yg)O_(zg) (xg satisfies 1≤xg≤3, yg satisfies 0≤yg≤2, and zg satisfies 1≤zg≤10); Li₃BO₃; Li₃BO₃—Li₂SO₄; Li₂O—B₂O₃—P₂O₅; Li₂O—SiO₂; Li₆BaLa₂Ta₂O₁₂; Li₃PO_((4-3/2w))N_(w) (w satisfies w<1); Li_(3.5)Zn_(0.25)GeO₄ having a lithium super ionic conductor (LISICON)-type crystal structure; La_(0.55)Li_(0.35)TiO₃ having a perovskite-type crystal structure; LiTi₂P₃O₁₂ having a natrium super ionic conductor (NASICON)-type crystal structure, Li_(1+xh+yh)(Al, Ga)_(xh)(Ti, Ge)_(2-xh)Si_(yh)P_(3-yh)O₁₂ (here, xh satisfies 0≤xh≤1 and yh satisfies 0≤yh≤1); Li₇La₃Zr₂O₁₂ having a garnet-type crystal structure. In addition, phosphorus compounds containing Li, P, and O are also desirable. Examples thereof include lithium phosphate (Li₃PO₄); LiPON in which some of oxygen atoms in lithium phosphate are substituted with nitrogen, LiPOD (D is at least one element selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, and Au), and the like. In addition, it is also possible to preferably use LiAON (A represents at least one selected from Si, B, Ge, Al, C, and Ga) and the like.

Among these, LLT, Li_(xb)La_(yb)Zr_(zb)M^(bb) _(mb)O_(nb) (M^(bb) is one or more elements selected from the group consisting of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In and Sn, xb satisfies 5≤xb≤10, yb satisfies 1≤yb≤4, zb satisfies 1≤zb≤4, mb satisfies 0≤mb≤2, and nb satisfies 5≤nb≤20.), LLZ, Li₃BO₃, Li₃BO₃—Li₂SO₄, and Li_(xd)(Al, Ga)_(yd)(Ti, Ge)_(zd)Si_(ad)P_(md)O_(nd) (here, xd satisfies 1≤xd≤3, yd satisfies 0≤yd≤1, zd satisfies 0≤zd≤2, ad satisfies 0≤ad≤1, md satisfies 1≤md≤7, and nd satisfies 3≤nd≤13) are preferred, and LLZ is more preferred. These compounds may be used singly or two or more compounds may be used in combination.

These inorganic solid electrolytes may be used singly or two or more inorganic solid electrolytes may be used in combination.

The average particle size of the inorganic solid electrolyte is not particularly limited, but is preferably 0.01 μm or more and more preferably 0.1 μm or more. The upper limit is preferably 100 μm or less and more preferably 50 μm or less.

When the satisfaction of both the battery performance and the interface resistance-reducing and maintaining effect is taken into account, the content of the inorganic solid electrolyte in the solid electrolyte composition for an all-solid state secondary battery is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 20% by mass or more with respect to 100% by mass of the solid components. From the same viewpoint, the upper limit is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and particularly preferably 99.0% by mass or less. Here, in the case of being used together with a positive electrode active material or a negative electrode active material described below, the total content is preferably in the above-described range.

Meanwhile, in the present specification, solid components refer to components that do not disappear due to volatilization or evaporation in the case of being dried at 170° C. for six hours and typically indicate components other than a dispersion medium described below.

Next, electrode active materials that are used in the solid electrolyte composition for an all-solid state secondary battery of the present invention will be described. Meanwhile, in the present specification, there will be cases in which a solid electrolyte composition for an all-solid state secondary battery for forming the positive electrode active material layer is referred to as a composition for a positive electrode. On the other hand, there will be cases in which a solid electrolyte composition for an all-solid state secondary battery for forming the negative electrode active material layer is referred to as a composition for a negative electrode.

(Positive Electrode Active Material)

A positive electrode active material that is used in the composition for a positive electrode for forming the positive electrode active material layer in the all-solid state secondary battery of the present invention will be described. The positive electrode active material is preferably a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. The above-described material is not particularly limited and may be transition metal oxides, elements capable of being complexed with Li such as sulfur, or the like. Among these, transition metal oxides are preferably used, and the transition metal oxides more preferably have a transition metal element M^(a) (one or more elements selected from Co, Ni, Fe, Mn, Cu, and V). In addition, a mixing element M^(b) (an element of Group I (Ia) of the periodic table other than lithium, and an element of Group II (IIa), Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, or the like) may also be mixed. Regarding the amount thereof mixed, the ratio of the mixing element M^(b) to the amount of the transition metal element M^(a) is preferably 0 to 30 mol %. A transition metal oxide synthesized by mixing Li and M^(a) so that the molar ratio of Li/M^(a) reaches 0.3 to 2.2 is more preferred.

Specific examples of the transition metal oxides include transition metal compounds having a bedded rock salt-type structure (MA), transition metal oxides having a spinel-type structure (MB), lithium-containing transition metal phosphoric acid compounds (MC), lithium-containing transition metal halogenated phosphoric acid compounds (MD), lithium-containing transition metal silicon oxides (ME), and the like.

(MA) Transition Metal Compounds Having Bedded Rock Salt-Type Structure

The transition metal compounds having a bedded rock salt-type structure are preferably transition metal compounds (electrode active material particles) having a bedded rock salt-type structure represented by Formula (B1).

Li_(a1)M¹O_(b1)  Formula (B1)

In Formula (B1), M¹ represents a metal including at least one of Co, Ni, Fe, Mn, Cu, or V, preferably, M¹ represents a metal including at least one selected from the group consisting of Co, Ni, Fe, Mn, Cu, and V, a1 represents 0 to 1.2, and b1 represents 1 to 3. M¹ may include the mixing element M^(b). Meanwhile, M¹ may be a metal obtained by mixing a plurality of metal elements so that the total of the molar ratio of individual elements of the plurality of metal elements reaches 1 such as LiNi_(0.85)Co_(0.1)Al_(0.05)O₂ described below (a metal obtained by mixing a plurality of metal elements so that the total of the molar ratio of individual elements reaches 0.99 or more such as NMC described below is also considered as the metal obtained by mixing a plurality of metal elements so that the total of the molar ratio reaches 1).

Specific examples of the transition metal compounds having a bedded rock salt-type structure represented by Formula (B1) include LiCoO₂ (lithium cobalt oxide [LCO]), LiNiO₂ (lithium nickelate), LiNi_(0.85)Co_(0.1)Al_(0.05)O₂ (lithium nickel cobalt aluminum oxide [NCA]), LiNi_(0.33)Co_(0.33)Mn_(0.33)O₂ (lithium nickel manganese cobalt oxide [NMC]), and LiNi_(0.5)Mn_(0.5)O₂ (lithium manganese nickelate).

(MB) Transition Metal Oxides Having Spinel-Type Structure

The transition metal oxides having a spinel-type structure are preferably transition metal oxides (electrode active material particles) having a spinel-type structure represented by Formula (B2).

Li_(c)M² _(m)O_(d1)  Formula (B2)

In Formula (B2), m1 represents an integer of 2 to 8, a plurality of M²'s each independently represents a metal including at least one of Co, Ni, Fe, Mn, Cu, Cr, or V, preferably represents a metal including at least one selected from the group consisting of Co, Ni, Fe, Mn, Cu, Cr, and V, c1 represents 0 to 2, and d1 represents 3 to 8. M² may include the mixing element M^(b)

Specific examples of the transition metal oxides having a spinel-type structure represented by Formula (B2) include LiCoMnO₄, Li₂FeMn₃O₈, Li₂CuMn₃O₈, Li₂CrMn₃O₈, and Li₂NiMn₃O₈.

(MC) Lithium-Containing Transition Metal Phosphoric Oxides

The lithium-containing transition metal phosphoric oxides are preferably lithium-containing transition metal phosphoric oxides (electrode active material particles) represented by Formula (B3).

Li_(e1)M³ _(m2)(PO₄)_(f1)  Formula (B3)

In Formula (B3), M³ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, preferably, M³ represents a metal including at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, m2 represents an integer of 1 to 8, e1 represents 0.1 to 3, and f1 represents 1 to 5. M³ may include the mixing element M^(b), and furthermore, M³ may be substituted with another metal such as Ti, Cr, Zn, Zr, or Nb. In a case in which a plurality of M³'s is present, the plurality of M³'s may be identical to or different from each other.

Examples of the lithium-containing transition metal phosphoric oxides represented by Formula (B3) include olivine-type iron phosphate salts such as LiFePO₄ and Li₃Fe₂(PO₄)₃, cobalt phosphates such as LiCoPO₄, and monoclinic nasicon-type vanadium phosphate salt such as Li₃V₂(PO₄)₃ (lithium vanadium phosphate). In addition, in the present invention, as the lithium-containing transition metal phosphoric oxide, it is also possible to use iron pyrophosphate such as LiFeP₂O₇.

(MD) Lithium-Containing Transition Metal Halogenated Phosphoric Oxides

The lithium-containing transition metal halogenated phosphoric oxides are preferably lithium-containing transition metal halogenated phosphoric oxides (electrode active material particles) represented by Formula (B4).

Li_(g1)M⁴(PO₄)_(h1)X_(i1)  Formula (B4)

In Formula (B4), M⁴ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, preferably, M⁴ represents a metal including at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, X represents a halogen element, g1 represents 0.1 to 3, h1 represents 1 to 5, and i1 represents 0.1 to 5. M⁴ may include the mixing element M^(b), and furthermore, M⁴ may be substituted with another metal such as Ti, Cr, Zn, Zr, or Nb.

Examples of the lithium-containing transition metal halogenated phosphoric oxides represented by Formula (B4) include iron fluorophosphates such as Li₂FePO₄F, manganese fluorophosphates such as Li₂MnPO₄F, cobalt fluorophosphates such as Li₂CoPO₄F.

(ME) Lithium-Containing Transition Metal Silicon Oxides

The lithium-containing transition metal silicon oxides are preferably lithium-containing transition metal silicon oxides (electrode active material particles) represented by Formula (B5).

Li_(j1)M⁵(SiO₄)_(k1)  Formula (B5)

In Formula (B5), M⁵ represents a metal including at least one of Co, Fe, Mn, Ni, Cu, or V, preferably, M⁵ represents a metal including at least one selected from the group consisting of Co, Fe, Mn, Ni, Cu, and V, j1 represents 0 to 3, and k1 represents 1 to 5. M⁵ may include the mixing element M^(b), and furthermore, M⁵ may be substituted with another metal such as Ti, Cr, Zn, Zr, or Nb.

Examples of the lithium-containing transition metal silicon oxides represented by Formula (B5) include Li₂FeSiO₄, Li₂MnSiO₄, Li₂CoSiO₄, and the like.

In the present invention, as the positive electrode active material, the electrode active material particles represented by any one of Formulae (B1) to (B5) are preferably used, the electrode active material particles represented by Formula (B1) are preferred, and LiCoO₂ and LiNi_(0.85)Co_(0.01)Al_(0.05)O₂ are particularly preferred.

The volume-average particle diameter (circle-equivalent average particle diameter) of the positive electrode active material that is used in the all-solid state secondary battery of the present invention is not particularly limited. For example, the volume-average particle diameter is preferably 0.1 μm to 50 μm. In order to provide a predetermined particle diameter to the positive electrode active material, an ordinary crusher or classifier may be used.

Positive electrode active materials obtained using a firing method may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent. As the average particle diameter of the positive electrode active material particles, the volume-average particle diameter (circle-equivalent average particle diameter) of positive electrode active material particles is measured using a laser diffraction/scattering-type particle size distribution measurement instrument LA-920 (trade name, manufactured by Horiba Ltd.).

The chemical formulae of positive electrode active materials obtained using the firing method can be computed using an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method or, as a convenient method, from the mass difference of powder before and after firing.

The content of the positive electrode active material is not particularly limited, but is preferably 10% to 90% by mass and more preferably 20% to 80% by mass with respect to 100% by mass of the solid components in the solid electrolyte composition for an all-solid state secondary battery for forming the positive electrode active material layer.

The positive electrode active material may be used singly or two or more positive electrode active materials may be used in combination.

In addition, to the positive electrode active material layer, an auxiliary conductive agent may be appropriately added as necessary. As the auxiliary conductive agent, it is possible to use the auxiliary conductive agents described below.

(Negative Electrode Active Material)

Next, a negative electrode active material that is used in the solid electrolyte composition for an all-solid state secondary battery for forming the negative electrode active material layer in the all-solid state secondary battery of the present invention will be described. The negative electrode active material is preferably a negative electrode active material capable of reversibly intercalating and deintercalating lithium ions. The above-described material is not particularly limited, and examples thereof include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal complex oxides, a lithium single body or lithium alloys such as lithium aluminum alloys, metals capable of forming alloys with lithium such as Sn, Si, and In, and the like. Among these, carbonaceous materials or metal complex oxides are preferably used in terms of reliability. In addition, the metal complex oxides are preferably capable of absorbing and deintercalating lithium. The materials are not particularly limited, but preferably contain titanium and/or lithium as constituent components from the viewpoint of high-current density charging and discharging characteristics.

The carbonaceous material that is used as the negative electrode active material is a material substantially including carbon. Examples thereof include petroleum pitch, natural graphite, artificial graphite such as highly oriented pyrolytic graphite, and carbonaceous material obtained by firing a variety of synthetic resins such as polyacrylonitrile (PAN)-based resins or furfuryl alcohol resins. Furthermore, examples thereof also include a variety of carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated polyvinyl alcohol (PVA)-based carbon fibers, lignin carbon fibers, glassy carbon fibers, and active carbon fibers, mesophase microspheres, graphite whisker, flat graphite, and the like.

The metal oxides and the metal complex oxides being applied as the negative electrode active material are particularly preferably amorphous oxides, and furthermore, chalcogenides which are reaction products between a metal element and an element belonging to Group XVI of the periodic table are also preferably used. The amorphous oxides mentioned herein refer to oxides having a broad scattering band having a peak of a 2θ value in a range of 20° to 40° in an X-ray diffraction method in which CuKα rays are used and may have crystalline diffraction lines. The highest intensity in the crystalline diffraction line appearing at the 2θ value of 40° or more and 70° or less is preferably 100 times or less and more preferably five times or less of the diffraction line intensity at the peak of the broad scattering line appearing at the 2θ value of 20° or more and 40° or less and particularly preferably does not have any crystalline diffraction lines.

In a compound group including the amorphous oxides and the chalcogenides, amorphous oxides of semimetal elements and chalcogenides are more preferred, and elements belonging to Groups XIII (IIIB) to XV (VB) of the periodic table, oxides including one element or a combination of two or more elements of Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi, and chalcogenides are particularly preferred. Specific examples of preferred amorphous oxides and chalcogenides include Ga₂O₃, SiO, GeO, SnO, SnO₂, PbO, PbO₂, Pb₂O₃, Pb₂O₄, Pb₃O₄, Sb₂O₃, Sb₂O₄, Sb₂O₅, Bi₂O₃, Bi₂O₄, SnSiO₃, GeS, SnS, SnS₂, PbS, PbS₂, Sb₂S₃, Sb₂S₅, SnSiS₃ and the like. In addition, these amorphous oxides may be complex oxides with lithium oxide, for example, Li₂SnO₂.

The negative electrode active material preferably contains a titanium atom. More specifically, Li₄Ti₅O₁₂ (lithium titanate [LTO]) is preferred since the volume fluctuation during the absorption and deintercalation of lithium ions is small and thus the high-speed charging and discharging characteristics are excellent and the deterioration of electrodes is suppressed, whereby it becomes possible to improve the service lives of lithium ion secondary batteries.

The average particle size of the negative electrode active material is preferably 0.1 μm to 60 μm. In order to provide a predetermined particle size, an ordinary crusher or classifier is used. For example, a mortar, a ball mill, a sand mill, an oscillatory ball mill, a satellite ball mill, a planetary ball mill, a swirling airflow-type jet mill, a sieve, or the like is preferably used. During crushing, it is also possible to carry out wet-type crushing in which water or an organic solvent such as methanol is made to coexist as necessary. In order to provide a desired particle diameter, classification is preferably carried out. The classification method is not particularly limited, and it is possible to use a sieve, a wind power classifier, or the like depending on the necessity. Both of dry-type classification and wet-type classification can be carried out.

The chemical formulae of the carbonaceous material obtained by firing a variety of synthetic resins can be computed using an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method or, as a convenient method, from the mass difference of powder before and after firing.

Preferred examples of negative electrode active materials that can be jointly used with amorphous oxide negative electrode active materials mainly containing Sn, Si, or Ge include carbonaceous materials capable of absorbing and deintercalating lithium ions or metallic lithium, lithium, lithium alloys, and metals capable of forming an alloy with lithium.

Among these, at least one negative electrode active material represented by Formula (A) is preferably included.

Si_(x)M_((1-x))  Formula (A)

In Formula (A), x represents a number of 0.01 or more and less than 1 and indicates a molar fraction. M represents any one of a chalcogen element, a semimetal element, an alkali metal element, an alkali earth metal element, and a transition metal element, or a combination thereof.

Preferably, M can be selected from chalcogen elements such as O, S, and Se, semimetal elements such as B and Ge, alkali metal elements such as Li and Na, alkali earth metal elements such as Mg and Ca, and transition metal elements such as Ti, V, Mn, Fe, Co, Ni, and Cu. In addition, M may be a combination of two or more of the above-described elements.

Among these, the chalcogen elements or the transition metal elements are preferred, and the transition metal elements are more preferred. Among the transition metal elements, first transition metal elements are preferred, Ti, V, Mn, Fe, Co, Ni, and Cu are more preferred, and Ti, Mn, Fe, Co, and Ni are particularly preferred.

x is preferably 0.1 or more and less than 1, more preferably 0.1 or more and 0.99 or less, still more preferably 0.2 or more and 0.98 or less, and particularly preferably 0.3 or more and 0.95 or less.

The negative electrode active material preferably contains a titanium atom. More specifically, Li₄Ti₅O₁₂ is preferred since the volume fluctuation during the absorption and deintercalation of lithium ions is small and thus the high-speed charging and discharging characteristics are excellent and the deterioration of electrodes is suppressed, whereby it becomes possible to improve the service lives of all-solid state secondary batteries.

The content of the negative electrode active material is not particularly limited, but is preferably 10 to 80% by mass and more preferably 20 to 70% by mass with respect to 100% by mass of the solid components in the solid electrolyte composition for an all-solid state secondary battery.

The negative electrode active material may be used singly or two or more negative electrode active materials may be used in combination.

In addition, to the negative electrode active material layer, an auxiliary conductive agent may be appropriately added as necessary. As the auxiliary conductive agent, it is possible to use the auxiliary conductive agents described below.

The surfaces of the positive electrode active material and the negative electrode active material may be surface-coated with another metal oxide. Examples of the surface coating agent include metal oxides which contain Ti, Nb, Ta, W, Zr, Si, or the like and, furthermore, may contain Li.

Examples of a method for coating the surfaces include the following methods which can be appropriately used in the present invention.

For example, positive electrode active material materials having a coating portion made of a lithium niobate-based compound formed on the surface of an oxide positive electrode active material are described in JP2010-225309A and a non-patent document of Narumi Ohta et al., “LiNbO₃-coated LiCoO₂ as cathode material for all solid-state lithium secondary batteries”, Electrochemistry Communications 9 (2007) 1486 to 1490.

In addition, as a coating material of the surface of a lithium metal oxide Li_(Y)XO_(Z) (in the formula, X¹ is Co, Mn, or Ni, and Y and Z are respectively an integer of 1 to 10) active material, JP2008-103280 exemplifies spinel titanate, tantalum-based oxides, niobium-based oxides, and the like and specifically exemplifies Li₄Ti₅O₁₂, LiTaO₃, LiNbO₃, LiAlO₂, Li₂ZrO₃, Li₂WO₄, Li₂TiO₃, Li₂B₄O₇, Li₃PO₄, Li₂MoO₄, LiBO₂, and the like.

Electrode materials for an all-solid state secondary battery that are surface-treated with sulfur and/or phosphorus are described in JP2008-027581A.

In addition, JP2001-052733A describes that a lithium chloride may be carried on the surface of an oxide positive electrode active material.

In the present invention, among the above-described negative electrode active materials, carbonaceous materials, tin, silicon, indium, and oxides and sulfides thereof are preferred, carbonaceous materials or negative electrode active materials containing a titanium atom are more preferred, and the above-described graphite (preferably natural graphite) or Li₄Ti₅O₁₂ (LTO) is particularly preferred.

(Auxiliary Conductive Agent)

Next, the auxiliary conductive agent that is used in the present invention will be described. Substances that are generally known as auxiliary conductive agents can be used. The auxiliary conductive agent may be, for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, Ketjen black, or furnace black, irregular carbon such as needle cokes, a carbon fiber such as a vapor-grown carbon fiber or a carbon nanotube, or a carbonaceous material such as graphene or fullerene, all of which are electron-conductive materials, and also may be metal powder or a metal fiber of copper, nickel, or the like, and a conductive polymer such as polyaniline, polypyrrole, polythiophene, polyacetylene, or a polyphenylene derivative may also be used. In addition, these auxiliary conductive agents may be used singly or two or more auxiliary conductive agents may be used.

In the present invention, acetylene black is preferably used.

<Particles for All-Solid State Secondary Battery>

In the particles for an all-solid state secondary battery of the present invention, the surfaces of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles are reformed, and thus the proportion of a nitrogen element in the element composition of the surface is 0.1 atm % or more. The particle surfaces are hydrophilized, whereby it is possible to improve the wettability of the particles and improve the bonding property and the adhesiveness. The improvement of the bonding property and the adhesiveness enables the improvement of handleability and manufacturing suitability in the production of all-solid state secondary batteries and electrode sheets for an all-solid state secondary battery.

In a case in which the proportion of a nitrogen element in the element composition of the surface is less than 0.1 atm %, adhesiveness between solid particles, between the layers, and between the layer and the collector is poor, the ion conductivity of all-solid state secondary batteries is insufficient, and it is not possible to obtain desired battery performance. The proportion of a nitrogen element in the element composition is preferably 0.5 atm % or more and more preferably 1.0 atm % or more. The upper limit is not particularly limited, but is preferably 50 atm % or less, more preferably 30 atm % or less, still more preferably less than 20 atm %, still more preferably 10 atm % or less, and still more preferably 7 atm % or less.

<Method for Reforming Particle Surfaces by Actinic Ray Exposure Treatment>

Hereinafter, inorganic solid electrolyte particles, electrode active material particles, or auxiliary conductive agent particles which are not yet subjected to surface reforming by a method described below will be simply referred to as particles.

Particle surfaces can be hydrophilized by exposing the surfaces of the particles to an actinic ray and adding a predetermined amount of nitrogen atom thereto.

The reason for hydrophilizing the surfaces of the particles is not only the removal of fat and oil such as organic substances attached to the particle surfaces but also the formation of bonds by a variety of groups and hetero atoms (for example, an oxygen atom and a nitrogen atom) on the particle surfaces due to the disassociation of covalent bonds or the generation of radicals by actinic ray energy and the resultant contact with the external air (Development of Technologies and Processes of Atmospheric Pressure Plasma (Akitoshi Okino, CMC Publishing Co., Ltd. (2011)) and Surface Treatment and Reforming Technologies of Inorganic Materials and Future Perspective: Metal, Ceramic, Glass (Eiji Kamijo/Yoshihiko Suzuki/Shou Fujisawa, CMC Publishing Co., Ltd. (2007))).

Preferred examples of the actinic ray in the present invention include an infrared ray, a microwave, an ultraviolet ray, excimer laser light, an electron beam (EB), an X-ray, a high-energy light ray having a wavelength of 50 nm or less (EUV or the like), plasma, and the like. The actinic ray is more preferably plasma and particularly preferably low-temperature atmospheric pressure plasma.

In the present invention, plasma is preferably used since the degree of hydrophilization is higher not only on the surfaces of particles irradiated with plasma but also in the surfaces compared with non-irradiated surfaces, and fine structures between particles are filled with gas, thereby exhibiting an effect of improving the bonding property.

The atmosphere for exposing the particles to the actinic ray is not particularly limited and may be a vacuum, the atmosphere, or other gaseous atmospheres. In order to make nitrogen present on the surfaces, nitrogen is preferably present.

The exposure time is not particularly limited, but is preferably 1 second to 24 hours, more preferably 5 seconds to 1 hour, and particularly preferably 10 seconds to 10 minutes.

For the introduction of an nitrogen element into the particle surfaces, there are a method in which the particle surfaces are treated with the actinic ray and then exposed to nitrogen (the air) and a method in which a nitrogen radical is directly sprayed (the actinic ray is radiated in a nitrogen atmosphere or plasma of a nitrogen-containing gas is radiated).

The content ratio of the nitrogen element can be obtained using an X-ray photoelectron spectroscopy (abbreviated as XPS or ESCA). An X-ray is radiated on a sample surface, and the energy of a photoelectron being generated is measured, whereby the constituent elements of the sample and the electron states thereof can be analyzed. From the energy intensity of the photoelectron being generated, the element ratio can be found.

Since the space resolution is approximately 1 to 10 μm, it is possible to identify which particle is measured even in a case in which the sample is a sheet of a powder composition in which a solid electrolyte and an active material are mixed together such as the electrode active material layer in an all-solid state secondary battery. In addition, the measurement depth is 1 to 10 nm, and it is possible to obtain the element composition of the outer surfaces of the particles for an all-solid state secondary battery.

Examples of a nitrogen element-containing functional group in a case in which the particle surface is hydrophilized and a nitrogen element is (directly) bonded to the particle include functional groups having a nitrogen atom (an amine, an amide, a nitro, urethane (R¹OC(═O)NR²R³), an imine (R⁴R⁵C═N—R⁶), an enamine (R⁷R⁸C═CR⁹—NR¹⁰R¹¹), an oxime (R¹²R¹³C═N—OR¹⁴), and a lactam (R¹⁵C(═O)NR¹⁶R¹⁷); R to R¹⁷ are a random organic group, these groups form a covalent bond with atoms present on the surfaces of the particles for an all-solid state secondary battery, and the like). These functional groups can be detected using a Raman microscope. Hereinafter, a relationship between the Raman shift and a peak being observed will be described.

3,200 cm⁻¹ to 3,800 cm⁻¹: N—H stretching vibration

2,000 cm⁻¹ to 2,280 cm⁻¹: C═N multiple bond stretching vibration, C≡N multiple bond stretching vibration

1,500 cm⁻¹ to 1,800 cm⁻¹: N—H bending vibration, N═O stretching vibration, N—O stretching vibration

1,020 cm⁻¹ to 1,250 cm⁻¹: C—N stretching vibration

In the present invention, it is preferable that the proportion of the nitrogen element in the element composition of the surface of at least one kind of particles for an all-solid state secondary battery is 0.1 atm % or more and one or more spectrum peaks are detected in any of the above-described ranges. From the detection of spectrum peaks, the presence of the nitrogen-containing functional groups can be confirmed, and it is found that the contribution of the hydrophilization effect is attributed to these functional groups.

Here, “spectrum peaks being detected” means a case in which the maximum value is “preferentially” present with respect to base lines connecting both ends of the respective ranges described above. “Being preferential” refers to certainty of the detection limit or more and the determination limit or more, and, in the present specification, “How to Consider Detection Limit and Determination Limit (analysis 2010 (5) p. 216)” is referred to.

The resolution of the Raman microscope is approximately 0.5 μm in the high-resolution region, and this Raman microscope has a resolution high enough to analyze the surface of each of the particles for an all-solid state secondary battery.

The actinic ray treatment can be carried out regardless of the state of the particles for an all-solid state secondary battery (a powder state or a state of being dispersed in a liquid such as a slurry). Furthermore, the actinic ray treatment can also be carried out on the surfaces of the particles for an all-solid state secondary battery even in a state in which the particles are included in the coated solid electrolyte layer or electrode active material layer.

Any actinic rays can be radiated even after the production of an all-solid state secondary battery as long as the actinic rays have a wavelength short enough to permeate an appearance agent such as a laminate film that protects the all-solid state secondary battery.

The plasma that is used in the present invention may be any of vacuum plasma or atmospheric pressure plasma. Among them, low-temperature atmospheric pressure plasma that is generated under a condition of near the atmospheric pressure is preferably used. For example, it is possible to use a non-equilibrium plasma jet, low-temperature plasma by alternating-current pulse discharging, powder plasma, in-liquid plasma, torch-type plasma, tube plasma, or the like, and, in any cases, it is preferable to use plasma generated under a condition of near the atmospheric pressure.

For the radiation of plasma, a variety of atmospheric pressure plasma devices can be used. For example, a device in which an inert gas having a pressure near the atmospheric pressure is caused to flow between electrodes coated with a dielectric body and intermittent discharging is carried out, thereby generating low-temperature atmospheric pressure plasma or the like is preferred.

As the plasma device, a variety of modification examples can be selected depending on intended uses or the like. More specific examples thereof include the device that is used for the base plasma treatment in JP2008-60115A, the normal-pressure plasma device described in JP2004-228136A, and the plasma devices described in the specifications of JP2006-21972A, JP2007-188690A, WO2005/062338A, WO2007/024134A, WO2007/145513A, and the like.

In addition, there are commercially available atmospheric pressure plasma devices, and, for example, it is also possible to preferably use atmospheric pressure plasma devices that are commercially available in the current market such as ATMP-1000 of Arios Inc., an atmospheric pressure plasma device of Heiden Laboratory Co., Ltd., an S5000 type atmospheric pressure low-temperature plasma jet device of Sakigake-Semiconductor Co., Ltd., powder plasma devices indicated as ASS-400 type, PPU-800 type, or SKIp-ZKB type, MyPL100 and ILP-1500 of Well Inc., and RD 550 of Sekisui Chemical Co., Ltd. (all are trade names). However, in order to alleviate damage to the solid electrolyte layer or the electrode active material layer by avoiding the uneven concentration (streamer) of plasma, it is preferable to use, for example, a device in which an effort is made for an electric circuit by conducting electricity to a discharging portion through a pulse control element which is described in WO2005/062338A and WO2007/024134A.

Meanwhile, the “pressure near the atmospheric pressure” in the “low-temperature atmospheric pressure plasma” in the present invention refers to a range of 70 kPa or more and 130 kPa or less and is preferably a range of 90 kPa or more and 110 kPa or less.

As a discharging gas that is used to generate the atmospheric pressure plasma, it is possible to use a gas of any of nitrogen, oxygen, hydrogen, argon (Ar), helium (He), ammonia, and carbon dioxide or a gas mixture of two or more thereof. A noble gas of He, Ar, or the like which is an inert gas or a nitrogen gas (N₂) is preferably used, and a noble gas of Ar or He is particularly preferred. In a case in which the plasma is applied to the surface of the solid electrolyte layer or the electrode active material layer, the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles in the solid electrolyte layer or the electrode active material layer are hydrophilized by the plasma. In a case in which the plasma is applied to the surface of the solid electrolyte layer or the electrode active material layer, the hydrophilization rapidly proceeds.

Meanwhile, the plasma treatment may be carried out in a batch manner or in an inline manner by being connected to another step.

From the viewpoint of suppressing damage to the solid electrolyte layer or the electrode active material layer, it is effective to separate a plasma action portion and the discharging portion or generate uniform plasma by suppressing the generation of the local concentration (streamer) of the plasma through an effort on a discharging circuit. Particularly, the generation of uniform plasma is preferred since a uniform plasma treatment across a large area is possible. The plasma action and the discharging portion are preferably separated from each other by transporting plasma generated by discharging to the surface of the solid electrolyte layer or the electrode active material layer using an air stream of an inert gas and bringing the plasma into contact with the surface, and, particularly, a so-called plasma jet method is preferred. In this case, a path (conduction tube) for transporting the inert gas including the plasma is preferably a dielectric body such as glass, porcelain, or an organic polymer. As the generation of uniform plasma, the method in which uniform glow plasma in which streamer is suppressed by conducting electricity to an electrode coated with a dielectric body through the pulse control element is generated, which is described in the specifications of WO2005/062338A and WO2007/024134A, is preferred.

The distance from a supply nozzle of the inert gas including the plasma to the surface of the solid electrolyte layer or the electrode active material layer is preferably 0.01 mm to 100 mm and more preferably 1 mm to 20 mm.

A region on which the plasma treatment is carried out may be sufficiently supplied with an inert gas or filled with an inert gas. During the above-described transportation of the plasma using an inert gas, it is preferable to make the inert gas flow to a plasma generation portion even before the lighting of the plasma and make the inert gas continuously flow even after the lighting of the plasma.

Regarding the inert gas after the plasma treatment, since the plasma has a short service life, the inert gas may be exhausted without carrying out any special treatments, but the inert gas that has been used for the treatment may also be collected by providing an air inlet near a treated region.

As the temperature during the radiation of the plasma, a random temperature can be selected depending on the characteristics of the material in the solid electrolyte layer or the electrode active material layer that is irradiated with the plasma, but a temperature at which an increase in the temperature by the radiation of the low-temperature atmospheric pressure plasma is small is preferred since damage can be alleviated. In a case in which the plasma-applied region is separated from a plasma generation device, the above-described effect further improves.

In the above-described method, the low-temperature atmospheric pressure plasma is selected and radiated, whereby the supply of heat energy from the plasma can be alleviated, and it is possible to suppress an increase in the temperature of the solid electrolyte layer or the electrode active material layer. An increase in the temperature of the solid electrolyte layer or the electrode active material layer by the irradiation with the plasma is preferably 50° C. or lower, more preferably 40° C. or lower, and particularly preferably 20° C. or lower.

The temperature during the radiation of the plasma is preferably a temperature or lower at which the material in the solid electrolyte layer or the electrode active material layer that is irradiated with the plasma is sustainable, generally, preferably −196° C. or higher and lower than 150° C. and more preferably −21° C. or higher and 100° C. or lower.

Furthermore, the temperature is preferably −10° C. or higher and 80° C. or lower and more preferably a temperature near room temperature (25° C.) which is under the ambient temperature atmosphere. The low-temperature atmospheric pressure plasma in the present invention refers to plasma that is radiated at 0° C. or higher and 50° C. or lower.

(Binder) The solid electrolyte composition for an all-solid state secondary battery of the present invention also preferably contains a binder.

The binder that is used in the present invention is not particularly limited as long as the binder is an organic polymer.

The binder that can be used in the present invention is preferably a binder that is generally used as a binding agent for positive electrodes or negative electrodes of battery materials, is not particularly limited, and is preferably, for example, a binder including resins described below.

Examples of fluorine-containing resins include polytetrafluoroethylene (PTFE), polyvinylene difluoride (PVdF), and copolymers of polyvinylene difluoride and hexafluoropropylene (PVdF-HFP).

Examples of hydrocarbon-based thermoplastic resins include polyethylene, polypropylene, styrene butadiene rubber (SBR), hydrogenated styrene butadiene rubber (HSBR), butylene rubber, acrylonitrile butadiene rubber, polybutadiene, polyisoprene, and the like.

Examples of acrylic resins include polymethyl (meth)acrylate, polyethyl (meth)acrylate, polyisopropyl (meth)acrylate, polyisobutyl (meth)acrylate, polybutyl (meth)acrylate, polyhexyl (meth)acrylate, polyoctyl (meth)acrylate, polydodecyl (meth)acrylate, polystearyl (meth)acrylate, poly 2-hydroxyethyl (meth)acrylate, poly(meth)acrylate, polybenzyl (meth)acrylate, polyglycidyl (meth)acrylate, polydimethylaminopropyl (meth)acrylate, and copolymers of monomers constituting the above-described resins.

In addition, copolymers with other vinyl-based monomers are also preferably used. Examples thereof include polymethyl (meth)acrylate-polystyrene copolymers, polymethyl (meth)acrylate-acrylonitrile copolymers, polybutyl (meth)acrylate-acrylonitrile-styrene copolymers, and the like.

Other than the radical polymerization-based polymer, a polycondensation-based polymer can also be used. As the polycondensation-based polymer, it is possible to preferably use a urethane resin, a urea resin, an amide resin, an imide resin, a polyester resin, or the like.

The polycondensation-based polymer preferably has a hard segment portion and a soft segment portion. The hard segment portion refers to a portion capable of forming an intermolecular hydrogen bond, and the soft segment portion generally refers to a flexible portion which has a glass transition temperature (Tg) of room temperature (25° C.±5° C.) or lower and a molecular weight of 400 or more.

The polycondensation-based polymers may be used singly or two or more polycondensation-based polymers may be used in combination.

Regarding the glass transition temperature of the binder, the upper limit is preferably 50° C. or lower, more preferably 0° C. or lower, and most preferably −20° C. or lower. The lower limit is preferably −100° C. or higher, more preferably −70° C. or higher, and particularly preferably −50° C. or higher.

The glass transition temperature (Tg) is measured using a dried specimen and a differential scanning calorimeter “X-DSC7000” (trade name, manufactured by SIINanoTechnology Inc.) under the following conditions. The glass transition temperature of the same specimen is measured twice, and the measurement result of the second measurement is employed.

Atmosphere of the measurement chamber: Nitrogen (50 mL/min)

Temperature-increase rate: 5° C./min

Measurement-start temperature: −100° C.

Measurement-end temperature: 200° C.

Specimen pan: Aluminum pan

Mass of the measurement specimen: 5 mg

Calculation of Tg: Tg is calculated by rounding off the middle temperature between the declination-start point and the declination-end point in the DSC chart to the integer.

A polymer constituting the binder that is used in the present invention preferably has a moisture concentration of 100 ppm or less (mass-based) and Tg of 100° C. or lower.

In addition, the polymer constituting the binder that is used in the present invention may be dried by being crystallized or may be used in a polymer solution form. The amount of a metal-based catalyst (tin, titanium, or bismuth catalyst which is an urethanization or polyesterification catalyst) is preferably small. The concentration of metal in copolymers is preferably set to 100 ppm or less (mass-based) by decreasing the amount of the metal during polymerization or removing the catalyst by means of crystallization.

The solvent that is used for the polymerization reaction of the polymer is not particularly limited. Meanwhile, solvents that do not react with the inorganic solid electrolyte or the active materials and furthermore do not decompose the inorganic solid electrolyte or the active materials are desirably used. For example, it is possible to use hydrocarbon-based solvents (toluene, heptane, and xylene), ester-based solvents (ethyl acetate and propylene glycol monomethyl ether acetate), ether-based solvents (tetrahydrofuran, dioxane, and 1,2-diethoxyethane), ketone-based solvents (acetone, methyl ethyl ketone, and cyclohexanone), nitrile-based solvents (acetonitrile, propionitrile, butyronitrile, and isobutyronitrile), and halogen-based solvents (dichloromethane and chloroform).

The mass average molecular weight of the polymer constituting the binder that is used in the present invention is preferably 10,000 or more, more preferably 20,000 or more, and still more preferably 50,000 or more. The upper limit is preferably 1,000,000 or less, more preferably 200,000 or less, and still more preferably 100,000 or less.

In the present invention, the molecular weight of the polymer refers to the mass average molecular weight unless particularly otherwise described. The mass average molecular weight can be measured as the polystyrene-equivalent molecular weight by means of GPC. At this time, the polystyrene-equivalent molecular weight is detected as RI using a GPC apparatus HLC-8220 (manufactured by Tosoh Corporation) and G3000HXL+G2000HXL as columns at a flow rate at 23° C. of 1 mL/min. An eluent can be selected from tetrahydrofuran (THF), chloroform, N-methyl-2-pyrrolidone (NMP), and m-cresol/chloroform (manufactured by Shonanwako Junyaku), and THF is used in a case in which the polymer needs to be dissolved.

In a case in which favorable interface resistance-reducing and maintaining properties are taken into account when the binder is used in all-solid state secondary batteries, the content of the binder in the solid electrolyte composition for an all-solid state secondary battery is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 1% by mass or more with respect to 100% by mass of the solid components. From the viewpoint of battery characteristics, the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less.

In the present invention, the mass ratio [(the mass of the inorganic solid electrolyte and the mass of the electrode active materials)/the mass of the binder] of the total mass of the inorganic solid electrolyte and the electrode active materials that are added as necessary to the mass of the binder is preferably in a range of 1,000 to 1. This ratio is more preferably 500 to 2 and still more preferably 100 to 10.

Furthermore, the binder preferably has a substituent X which is an acidic group. This is because the particle surfaces are modified with a nitrogen atom and exhibit basicity, and thus the ionic interaction with acidic groups becomes stronger, and thus a stronger bonding property can be developed.

The substituent X represents a group containing a functional group having a pKa of 14 or less (functional group X), and the pKa of the substituent X is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less. The lower limit of the pKa is preferably −10 or more, more preferably −5 or more, and particularly preferably 0 or more. The “pKa” mentioned herein is a value according to the definition described in Chemistry Handbooks (II) (4^(th) revised edition, 1993, The Chemistry Society of Japan, Maruzen-Yushodo Company, Limited). The measurement temperature is set to 25° C. in terms of the water temperature.

The structure of the functional group X having a pKa of 14 or less is not particularly limited as long as the functional group has physical properties that satisfy the above-described condition. Specific examples thereof include a carboxy group (having a pKa of approximately 3 to 5), a sulfonic acid group (having a pKa of approximately −3 to −2), a phosphoric acid group (having a pKa of approximately 2), —COCH₂CO—R¹ (having a pKa of approximately 8 to 10, R¹ represents hydroxy, alkoxy, or aryloxy), —COCH₂CN (having a pKa of approximately 8 to 11), —CONHCO—R² (R² represents hydroxy, alkoxy, or aryloxy), a phenolic hydroxyl group, —R_(F)CH₂OH, —(R_(F))₂CHOH (R_(F) represents a perfluoroalkyl group, the pKa is approximately 9 to 11)), a sulfonamide group (having a pKa of approximately 9 to 11), and the like, and particularly, a carboxy group, a sulfonic acid group, a phosphoric acid group (preferably a phosphoric acid group having an ethyl group), and —COCH₂CO—R² are preferred.

Meanwhile, in the case of obtaining the pKa through calculation, it is possible to use values computed using ACD/Labs (trade name, manufactured by Advanced Chemistry Development, Inc.) or the like. The calculation examples of typical functional groups X will be described below.

Substituent pKa —COOH 4.14 —SO₃H −2.80 —PO₄H₂ 2.12 (7.06 in the second calculation)

The binder that is used in the present invention is also preferably polymer particles holding a particle shape. In the present invention, polymethyl (meth)acrylate (PMMA), a poly(methyl methacrylate-methacrylic acid) copolymer (PMMA-PMA), or a poly(methyl methacrylate-ethyl methacrylate phosphate) copolymer (PMMA-PHM) is preferably used.

Here, the “polymer particles” refer to polymer particles which do not fully dissolve even in the case of being added to a dispersion medium described below, disperse in the dispersion medium while maintaining the particle shape, and have an average particle diameter of more than 0.01 μm.

The shape of the polymer particles is not limited as long as the polymer particles hold a solid form. The polymer particles may be monodispersed or polydispersed. The polymer particle may have a truly spherical shape or a flat shape and furthermore may have an irregular shape. The surface of the polymer particle may be flat or form an uneven shape. The polymer particle may have a core shell structure, and the core (inner core) and the shell (outer shell) may be constituted of the same material or different materials. In addition, the polymer particle may be hollow, and the ratio of being hollow is not limited.

The polymer particles can be synthesized using a method in which the polymer particles are polymerized in the presence of a surfactant, an emulsifier, or a dispersant or a method in which the polymer particles are precipitated in a crystal shape as the molecular weight increases.

In addition, an existing method in which a polymer is mechanically crushed or an existing method in which a polymer liquid is re-deposited, thereby producing fine particles may also be used.

The average particle diameter of the polymer particles is preferably 0.01 μm to 100 μm, more preferably 0.05 μm to 50 μm, still more preferably 0.1 μm to 20 μm, and particularly preferably 0.2 μm to 10 μm.

The average particle diameter of the polymer particles that are used in the present invention refers to an average particle diameter according to measurement conditions and a definition described below unless particularly otherwise described.

One percent by mass of a dispersion liquid is diluted and prepared using the polymer particles and a random solvent (a dispersion medium that is used to prepare the solid electrolyte composition for an all-solid state secondary battery, for example, heptane) in a 20 ml sample bottle. The diluted dispersion specimen is irradiated with 1 kHz ultrasonic waves for 10 minutes and then immediately used for testing. Data capturing is carried out 50 times using this dispersion liquid specimen, a laser diffraction/scattering-type particle size distribution measurement instrument LA-920 (trade name, manufactured by Horiba Ltd.), and a quartz cell for measurement at a temperature of 25° C., and the obtained volume-average particle diameter is considered as the average particle diameter. Regarding other detailed conditions and the like, the description of JIS Z8828:2013 “Particle size analysis-Dynamic light scattering method” is referred to as necessary. Five specimens are produced and measured per level, and the average values thereof are employed.

Meanwhile, the average particle diameter can be measured from the produced all-solid state secondary battery by, for example, disassembling the battery, peeling the electrodes, measuring the average particle diameters of the electrode materials according to the above-described method for measuring the average particle diameter of the polymer particles, and subtracting the measurement value of the average particle diameter of particles other than the polymer particles which has been measured in advance.

Meanwhile, as the binder that is used in the present invention, commercially available products can be used. In addition, the binder can also be prepared using an ordinary method.

(Lithium Salt)

The solid electrolyte composition for an all-solid state secondary battery of the present invention also preferably contains a lithium salt.

The lithium salt is preferably a lithium salt that is ordinarily used in this kind of products and is not particularly limited. Examples thereof include LiTFSI and the lithium salts described in paragraphs 0082 to 0085 of JP2015-088486A. In the present invention, LiTFSI is preferably used.

The content of the lithium salt is preferably 0 parts by mass or more and more preferably 5 parts by mass or more with respect to 100 parts by mass of the solid electrolyte.

The upper limit is preferably 50 parts by mass or less and more preferably 20 parts by mass or less.

(Dispersant)

The composition for an all-solid state secondary battery of the present invention preferably contains a dispersant. Since the particle surfaces are hydrophilization-treated, the wettability with the dispersant is improved, and thus the containment of the dispersant is preferred from the viewpoint of improving the bonding property.

The dispersant preferably includes a low-molecular-weight molecule or an oligomer having a molecular weight of 200 or more and less than 3,000 and preferably contains at least one selected from a group of functional groups (I) below and an alkyl group having 8 or more carbon atoms or an aryl group having 10 or more carbon atoms in the same molecule.

Group of functional groups (I): an acidic group, a group having a basic nitrogen atom, a (meth)acryl group, a (meth)acrylamide group, an alkoxysilyl group, an epoxy group, an oxetanyl group, an isocyanate group, a cyano group, a thiol group, and a hydroxy group

The molecular weight of the dispersant is more preferably 300 or more and less than 2,000 and particularly preferably 500 or more and less than 1,000. In a case in which the molecular weight is less than the upper limit value, the particles do not easily agglomerate, and it is possible to effectively suppress a decrease of the output. In addition, in a case in which the molecular weight is equal to or more than the lower limit value, the dispersant does not easily volatilize in a stage of the application and drying of a solid electrolyte composition slurry for an all-solid state secondary battery.

Among the group of functional groups (I), acidic groups (for example, a carboxy group, a sulfonic acid group, and a phosphoric acid group), groups having a basic nitrogen atom (for example, an amino group), or a cyano group are preferred, and acidic groups are more preferred. Among acidic groups, a carboxy group is particularly preferred.

The dispersant has an alkyl group having 8 or more carbon atoms or an aryl group having 10 or more carbon atoms.

The alkyl group having 8 or more carbon atoms needs to be an alkyl group having a total of 8 or more carbon atoms, may be linear, branched, or cyclic, and may contain a hetero atom between carbon-carbon bonds even in a case in which the alkyl group is not a hydrocarbon. In addition, the alkyl group having 8 or more carbon atoms may be unsubstituted or may further have a substituent, and, in the case of having a substituent, the substituent is preferably a halogen atom. Furthermore, the alkyl group may have an unsaturated carbon-carbon bond in the middle.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like, and a fluorine atom is preferred.

The alkyl group having 8 or more carbon atoms is preferably an alkyl group having 8 or more and 50 or less carbon atoms, more preferably an alkyl group having 8 or more and 30 or less carbon atoms, still more preferably an alkyl group having 8 or more and 20 or less carbon atoms, and particularly preferably an alkyl group having 8 or more and 18 or less carbon atoms.

Specific examples thereof include a normal octyl group, a normal decyl group, a normal dodecyl group, a normal tetradecyl group, a normal hexadecyl group, a stearyl group, a lauryl group, a linole group, a linolen group, a 2-ethylhexyl group, a 2-ethyloctyl group, a 2-ethyldodecyl group, a polyethylene glycol monomethyl group, a perfluorooctyl group, a perfluorododecyl group, and the like.

Among these, a normal octyl group, a 2-ethylhexyl group, a normal nonyl group, a normal decyl group, a normal undecyl group, a normal dodecyl group, a normal tetradecyl group, and a normal octadecyl group (a stearyl group) are preferred.

In a case in which the alkyl group having 8 or more carbon atoms has a substituent, examples of the substituent include an aryl group having 6 or more carbon atoms such as a phenyl group or a naphthyl group, a halogen atom, and the like. For example, the alkyl group may be an alkyl group substituted with an aryl group or a halogenated alkyl group substituted with a halogen.

The aryl group having 10 or more carbon atoms needs to be an aryl group having 10 or more carbon atoms in total and may contain a hetero atom between carbon-carbon bonds even in a case in which the aryl group is not a hydrocarbon. In addition, the aryl group having 10 or more carbon atoms may be unsubstituted or may further have a substituent, and, in the case of further having a substituent, the substituent is preferably a halogen atom.

The aryl group having 10 or more carbon atoms is preferably an aryl group having 10 or more and 50 or less carbon atoms, more preferably an aryl group having 10 or more and 30 or less carbon atoms, still more preferably an aryl group having 10 or more and 20 or less carbon atoms, and particularly preferably an aryl group having 10 or more and 18 or less carbon atoms.

Specific examples thereof include a naphthyl group, an anthracenyl group, a pyrenyl group, a terphenyl group, a naphthacenyl group, a pentacenyl group, a benzopyrenyl group, a chrysenyl group, a triphenylenyl group, a corannulenyl group, a coronenyl group, an ovalenyl group, and the like.

Among these, a condensed ring-type aromatic hydrocarbon group is preferred.

In a case in which the aryl group having 10 or more carbon atoms has a substituent, examples of the substituent include alkyl groups having 8 or more carbon atoms such as a normal octyl group, a halogen atom, and the like. For example, the aryl group may be an aryl group substituted into an alkyl group.

A particularly preferred combination is a combination of a carboxy group and the alkyl group having 8 or more carbon atoms in the same molecule, and specifically, it is possible to preferably use a long-chain saturated fatty acid and a long-chain unsaturated fatty acid.

The dispersant more preferably has two or more groups represented by the group of functional groups (I) in the same molecule and two or more alkyl groups having 8 or more carbon atoms or aryl groups having 10 or more carbon atoms.

(Dispersion Medium)

The solid electrolyte composition for an all-solid state secondary battery of the present invention may contain a dispersion medium. The dispersion medium needs to be capable of dispersing the respective components described above, and specific examples thereof include the following media.

Examples of alcohol compound solvents include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, t-butanol, ethylene glycol, propylene glycol, glycerin, 1,6-hexanediol, cyclohexanediol, sorbitol, xylitol, 2-methyl-2,4-pentanediol, 1,3-butanediol, and 1,4-butanediol.

Examples of ether compound solvents include alkylene glycol alkyl ethers (ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol, dipropylene glycol, propylene glycol monomethyl ether, propylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether (diglyme), triethylene glycol, polyethylene glycol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, diethylene glycol monobutyl ether, and the like), dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, cyclohexyl methyl ether, t-butyl methyl ether, tetrahydrofuran, and dioxane.

Examples of amide compound solvents include N,N-dimethylformamide, 1-methyl-2-pyrrolidone, 2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropanamide, and hexamethylphosphoric triamide.

Examples of amino compound solvents include triethylamine, diisopropylethylamine, and tributylamine.

Examples of ketone compound solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and diisobutyl ketone.

Examples of aromatic compound solvents include benzene, toluene, and xylene.

Examples of ester compound solvents include ethyl acetate, propyl acetate, butyl acetate, ethyl formate, propyl formate, butyl formate, ethyl lactate, propylene glycol monomethyl ether acetate, methyl isobutyrate, isopropyl isobutyrate, methyl pivalate, and isopropyl cyclohexanecarboxylate.

Examples of aliphatic compound solvents include pentane, hexane, heptane, octane, decane, and cyclohexane.

Examples of nitrile compound solvents include acetonitrile, propionitrile, and butyronitrile.

One kind of the dispersion medium may be used singly or two or more kinds of the dispersion media may be used in combination.

The boiling points of the dispersion medium at normal pressure (one atmosphere) are preferably 50° C. or higher and more preferably 70° C. or higher. The upper limit is preferably 250° C. or lower and more preferably 220° C. or lower.

In the present invention, at least one compound solvent of an alcohol compound solvent (preferably t-butanol), an ether compound solvent (preferably dibutyl ether, propylene glycol dimethyl ether, or diglyme), an amide compound solvent (preferably N,N-dimethylformamide), an aromatic compound solvent (preferably toluene), an ester compound solvent (preferably propylene glycol monomethyl ether acetate), or an aliphatic compound solvent (preferably heptane) is preferably used. In the present invention, as the dispersion medium, at least one of an ester compound solvent or a hydrocarbon-based solvent is preferably used, and a hydrocarbon-based solvent is particularly preferred. Examples of the hydrocarbon-based solvent include the aromatic compound solvent and the aliphatic compound solvent.

The use of the dispersion medium enables the prevention of the deterioration of the inorganic solid electrolyte and the obtainment of compositions in which the solid particles are dispersed.

(Moisture Content of Solid Electrolyte Composition for All-Solid State Secondary Battery)

The moisture content of the solid electrolyte composition for an all-solid state secondary battery of the present invention, that is, the moisture content as the solid electrolyte composition for an all-solid state secondary battery containing the dispersion medium is preferably 50 ppm or less, more preferably 40 ppm or less, and still more preferably 30 ppm or less. The lower limit value of the moisture content is not particularly limited, but is realistically 0.001 ppm or more.

Meanwhile, the moisture content of the solid electrolyte composition for an all-solid state secondary battery can be measured using the Karl Fischer method. As the measurement instrument, for example, a moisture meter CA-200 (trade name, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) can be used, and, as the Karl Fischer solution, AQUAMICRON AX (trade name, manufactured by Mitsubishi Chemical Corporation) can be used.

The moisture content in the above-described preferred range enables the suppression of reactions between a sulfide-based inorganic solid electrolyte and water in a case in which the sulfide-based inorganic solid electrolyte is used as the inorganic solid electrolyte.

The content of the dispersion medium is preferably 10 to 300 parts by mass and more preferably 50 to 150 parts by mass with respect to 100 parts by mass of the total solid content mass of the solid electrolyte composition for an all-solid state secondary battery.

<Collector (Metal Foil)>

The collector of the positive electrode and the collector of the negative electrode are preferably electron conductors. The collector of the positive electrode is preferably a collector obtained by treating the surface of an aluminum or stainless steel collector with carbon, nickel, titanium, or silver in addition to an aluminum collector, a stainless steel collector, a nickel collector, a titanium collector, or the like, and, among these, an aluminum collector and an aluminum alloy collector are more preferred. The collector of the negative electrode is preferably an aluminum collector, a copper collector, a stainless steel collector, a nickel collector, or a titanium collector and more preferably an aluminum collector, a copper collector, or a copper alloy collector.

Regarding the shape of the collector, generally, collectors having a film sheet-like shape are used, but it is also possible to use net-shaped collectors, punched collectors, compacts of lath bodies, porous bodies, foaming bodies, or fiber groups, and the like.

The thickness of the collector is not particularly limited, but is preferably 1 μm to 500 μm. In addition, the surface of the collector is preferably provided with protrusions and recesses by means of a surface treatment.

<Production of All-Solid State Secondary Battery>

The all-solid state secondary battery may be produced using an ordinary method.

Specific examples thereof include a method in which the solid electrolyte composition for an all-solid state secondary battery of the present invention is applied onto a metal foil which serves as the collector, thereby producing an electrode sheet for an all-solid state secondary battery on which a coated film is formed.

In the all-solid state secondary battery of the present invention, the electrode layers contain active materials. From the viewpoint of improving ion conductivity, the electrode layers preferably contain the inorganic solid electrolyte. In addition, from the viewpoint of improving the bonding properties between solid particles, between the individual layers, and between the electrode active material layer and the collector, the electrode layers preferably contain the binder.

The solid electrolyte layer contains the inorganic solid electrolyte. From the viewpoint of improving the bonding properties between solid particles and between layers, the solid electrolyte layer also preferably contains the binder.

For example, the solid electrolyte composition for an all-solid state secondary battery of the present invention which serves as a positive electrode material is applied onto a metal foil which is a positive electrode collector so as to form a positive electrode active material layer, thereby producing a positive electrode sheet for an all-solid state secondary battery. A composition for forming the solid electrolyte layer is applied onto the positive electrode active material layer, thereby forming a solid electrolyte layer. Furthermore, the solid electrolyte composition for an all-solid state secondary battery of the present invention which serves as a negative electrode material is applied onto the solid electrolyte layer, thereby forming a negative electrode active material layer. A collector on the negative electrode side (metal foil) is overlaid on the negative electrode active material layer, whereby it is possible to obtain a structure of an all-solid state secondary battery in which the solid electrolyte layer is sandwiched between a positive electrode layer and a negative electrode layer.

Meanwhile, the respective compositions described above may be applied using an ordinary method. At this time, the solid electrolyte composition for an all-solid state secondary battery of the present invention for forming the positive electrode active material layer, the composition for forming the inorganic solid electrolyte layer, and the solid electrolyte composition for an all-solid state secondary battery of the present invention for forming the negative electrode active material layer may be dried after being applied respectively or may be dried after being applied to multiple layers.

The drying temperature is not particularly limited. Meanwhile, the lower limit is preferably 30° C. or higher and more preferably 60° C. or higher, and the upper limit is preferably 300° C. or lower and more preferably 250° C. or lower. In a case in which the compositions are heated in the above-described temperature range, it is possible to remove the dispersion medium and form a solid state.

[Usages of All-Solid State Secondary Battery]

The all-solid state secondary battery of the present invention can be applied to a variety of usages. Application aspects are not particularly limited, and, in the case of being mounted in electronic devices, examples thereof include notebook computers, pen-based input personal computers, mobile personal computers, e-book players, mobile phones, cordless phone handsets, pagers, handy terminals, portable faxes, mobile copiers, portable printers, headphone stereos, video movies, liquid crystal televisions, handy cleaners, portable CDs, mini discs, electric shavers, transceivers, electronic notebooks, calculators, portable tape recorders, radios, backup power supplies, memory cards, and the like. Additionally, examples of consumer usages include automobiles, electric vehicles, motors, lighting equipment, toys, game devices, road conditioners, watches, strobes, cameras, medical devices (pacemakers, hearing aids, shoulder massage devices, and the like), and the like.

Furthermore, the all-solid state secondary battery can be used for a variety of military usages and universe usages. In addition, the all-solid state secondary battery can also be combined with solar batteries.

According to the preferred embodiment of the present invention, individual application forms as described below are derived.

[1] Solid electrolyte compositions for an all-solid state secondary battery including inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table, electrode active material particles, and auxiliary conductive agent particles, in which the proportion of a nitrogen element in the element composition of the surface of each of the inorganic solid electrolyte particles, the electrode active material particles, and the auxiliary conductive agent particles is 0.1 atm % or more (compositions for an electrode that is a positive electrode or negative electrode).

[2] Electrode sheets for an all-solid state secondary battery including inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table, electrode active material particles, and auxiliary conductive agent particles, in which the proportion of a nitrogen element in the element composition of the surface of each of the inorganic solid electrolyte particles, the electrode active material particles, and the auxiliary conductive agent particles is 0.1 atm % or more.

[3] All-solid state secondary batteries constituted using the above-described electrode sheet for an all-solid state secondary battery.

[4] Methods for manufacturing an electrode sheet for an all-solid state secondary battery in which the solid electrolyte composition for an all-solid state secondary battery is applied onto a metal foil, thereby forming a film.

[5] Methods for manufacturing an electrode sheet for an all-solid state secondary battery in which a wet slurry of the solid electrolyte composition for an all-solid state secondary battery is applied.

[6] Methods for manufacturing an all-solid state secondary battery in which all-solid state secondary batteries are manufactured using the method for manufacturing an electrode sheet for an all-solid state secondary battery.

Meanwhile, examples of the methods in which the solid electrolyte composition for an all-solid state secondary battery of the present invention is applied onto a collector include coating (wet-type coating, spray coating, spin coating, slit coating, stripe coating, bar coating, or dip coating), and wet-type coating (coating) is preferred.

All-solid state secondary batteries refer to secondary batteries having a positive electrode, a negative electrode, and an electrolyte which are all constituted of solid. In other words, all-solid state secondary batteries are differentiated from electrolytic solution-type secondary batteries in which a carbonate-based solvent is used as an electrolyte. Among these, the present invention is assumed to be an inorganic all-solid state secondary battery.

All-solid state secondary batteries are classified into organic (polymer) all-solid state secondary batteries in which a polymer compound such as polyethylene oxide is used as an electrolyte and inorganic all-solid state secondary batteries in which the Li—P—S-based glass, LLT, LLZ, or the like is used. Meanwhile, the application of polymer compounds to inorganic all-solid state secondary batteries is not inhibited, and polymer compounds can also be applied as binders of positive electrode active materials, negative electrode active materials, and inorganic solid electrolytes.

Inorganic solid electrolytes are differentiated from electrolytes in which the above-described polymer compound is used as an ion conductive medium (polymer electrolyte), and inorganic compounds serve as ion conductive media. Specific examples thereof include the Li—P—S-based glass, LLT, and LLZ. Inorganic solid electrolytes do not deintercalate positive ions (Li ions) and exhibit an ion transportation function. In contrast, there are cases in which materials serving as an ion supply source which is added to electrolytic solutions or solid electrolyte layers and deintercalates positive ions (Li ions) are referred to as electrolytes; however, in the case of being differentiated from electrolytes as the ion transportation materials, the materials are referred to as “electrolyte salts” or “supporting electrolytes”. Examples of the electrolyte salts include LiTFSI.

In the present invention, “compositions” refer to mixtures obtained by uniformly mixing two or more components. Here, compositions may partially include agglomeration or uneven distribution as long as the compositions substantially maintain uniformity and exhibit desired effects.

EXAMPLES

Hereinafter, the present invention will be described in more detail on the basis of examples. Meanwhile, the present invention is not interpreted to be limited thereto. In the following examples, “parts” and “%” are mass-based unless particularly otherwise described.

In addition, “−” used in the tables indicates that the corresponding components are not included in compositions of examples or the like. In addition, room temperature refers to 25° C.

<Synthesis of Sulfide-Based Inorganic Solid Electrolyte>

—Synthesis of Li—P—S-Based Glass—

As a sulfide-based inorganic solid electrolyte, Li—P—S-based glass was synthesized with reference to a non-patent document of T. Ohtomo, A. Hayashi, M. Tatsumisago, Y. Tsuchida, S. HamGa, K. Kawamoto, Journal of Power Sources, 233, (2013), pp. 231 to 235 and A. Hayashi, S. Hama, H. Morimoto, M. Tatsumisago, T. Minami, Chem. Lett., (2001), pp. 872 and 873.

Specifically, in a glove box under an argon atmosphere (dew point: −70° C.), lithium sulfide (Li₂S, manufactured by Aldrich-Sigma, Co. LLC. Purity: >99.98%) (2.42 g) and diphosphorus pentasulfide (P₂S₅, manufactured by Aldrich-Sigma, Co. LLC. Purity: >99%) (3.90 g) were respectively weighed, injected into an agate mortar, and mixed using an agate muddler for five minutes. Meanwhile, the mixing ratio between Li₂S and P₂S₅(Li₂S:P₂S₅) was set to 75:25 in terms of molar ratio.

66 zirconia beads having a diameter of 5 mm were injected into a 45 mL zirconia container (manufactured by Fritsch Japan Co., Ltd.), the full amount of the mixture of the lithium sulfide and the diphosphorus pentasulfide was injected thereinto, and the container was sealed in an argon atmosphere. The container was set in a planetary ball mill P-7 (trade name) manufactured by Fritsch Japan Co., Ltd., mechanical milling was carried out at a temperature of 25° C. and a rotation speed of 510 rpm for 20 hours, thereby obtaining yellow powder (6.20 g) of a sulfide solid electrolyte (Li—P—S-based glass).

<Surface Treatment of Particles>

—UV Treatment—

[Preparation of Particles NR-11]

Lithium cobalt oxide powder (LiCoO₂ (LCO)) (20 g) was broken onto a TEFLON (registered trademark, E. I. du Pont de Nemours and Company) bat so as to become uniform and put into a UV treatment device OPL1102 (trade name, manufactured by Mario Network Co., Ltd.), and a nitrogen gas was blown into the device at room temperature for 10 minutes so as to form a nitrogen atmosphere. The powder was irradiated with UV for 60 minutes, thereby obtaining surface-treated LCO powder.

The proportion of a nitrogen element in the particle surface was obtained using XPS (trade name: PHI 5000 VersaProbe II, manufactured by Ulvac-Phi. Incorporated) and the above-described computation method and found out to be 0.6 atm %.

In addition, a new peak was detected in a region (I) (3,200 cm⁻¹ to 3,800 cm⁻¹) using a Raman microscope spectrum device (trade name: LabRAM HR Revolution, manufactured by Horiba Ltd.), and it was confirmed that nitrogen-containing functional groups were directly bonded to the particle surfaces of LCO. Particles NR-11 having reformed particle surfaces of LCO were obtained in the above-described manner.

Particles NR-21, Particles NR-31, Particles NR-41, Particles NR-51, Particles NR-61, and Particles NR-62 shown in Table 1 below were obtained in the same manner.

—Electron Beam (EB) Treatment—

[Preparation of Particles NR-12]

LCO powder (20 g) was broken onto a TEFLON bat so as to become uniform, put into an EB treatment device EC250/15/180L (trade name, manufactured by Eye Electron Beam Co., Ltd.), and irradiated with an electron beam at room temperature in a vacuum state for 20 minutes, thereby obtaining surface-treated LCO powder.

The proportion of a nitrogen element in the particle surface was obtained using XPS and the above-described computation method and found out to be 0.3 atm %.

In addition, a new peak was detected in a region (I) using a Raman microscope spectrum device, and it was confirmed that nitrogen-containing functional groups were directly bonded to the particle surfaces. Particles NR-12 having reformed particle surfaces of LCO were obtained in the above-described manner.

Particles NR-52 and Particles NR-63 shown in Table 1 below were obtained in the same manner.

—Low-Temperature Atmospheric Pressure Plasma Treatment Method—

[Preparation of Particles NR-13]

LCO powder (20 g) was added to an atmospheric pressure powder plasma device ASS-400 (trade name, manufactured by Sakigake-Semiconductor Co., Ltd.) and irradiated with nitrogen plasma as low-temperature atmospheric pressure plasma for 20 minutes. The irradiation conditions are described below.

<Irradiation Conditions>

Irradiation temperature: Room temperature (25° C.)

Distance between LCO powder and nozzle of atmospheric pressure powder plasma device: 100 mm

Flow rate of nitrogen gas: 0.5 L/min

Output: 250 W

Rotation speed: 4 rpm

Pressure: 100 kPa

For the powder after the irradiation with the low-temperature atmospheric pressure plasma, the proportion of a nitrogen element in the particle surface was obtained using XPS and the above-described computation method and found out to be 1.2 atm %.

In addition, new peaks were detected in the region (I), a region (III) (1,500 cm⁻¹ to 1,800 cm⁻¹), and a region (IV) (1,020 cm⁻¹ to 1,250 cm⁻¹) using the Raman microscope spectrum device, and it was confirmed that nitrogen-containing functional groups were directly bonded to the particle surfaces of LCO. Particles NR-13 having reformed particle surfaces of LCO were obtained in the above-described manner.

Particles NR-22, Particles NR-32, Particles NR-33, Particles NR-42, Particles NR-43, Particles NR-53, Particles NR-64, and Particles NR-65 shown in Table 1 below were obtained in the same manner.

TABLE 1 Surface treatment method XPS Particles Particles Treatment Surface nitrogen Presence and absence of Raman (after (before time element proportion spectrum peak reforming) reforming) Actinic ray Atmosphere (minutes) (atm %) (I) (II) (III) (IV) R-1 LCO No treatment — — 0.0 Absent Absent Absent Absent NR-11 (positive UV Nitrogen gas 60 0.6 Present Absent Absent Absent NR-12 electrode EB Vacuum 20 0.3 Present Absent Absent Absent NR-13 active material) Atmospheric pressure Nitrogen gas 20 1.2 Present Absent Present Present plasma R-2 NCA No treatment — — 0.0 Absent Absent Absent Absent NR-21 (positive UV Air 60 0.3 Present Absent Present Absent NR-22 electrode Atmospheric pressure Nitrogen gas 20 0.9 Present Absent Present Present active material) plasma R-3 LLZ No treatment — — 0.0 Absent Absent Absent Absent NR-31 (oxide-based UV Nitrogen gas 240  0.7 Present Absent Absent Absent NR-32 inorganic solid Atmospheric pressure Nitrogen gas 60 1.3 Present Absent Present Present electrolyte) plasma NR-33 Atmospheric pressure Nitrogen (98%)/ 60 2.5 Present Present Present Present plasma hydrogen (2%) gas R-4 Li—P—S No treatment — — 0.0 Absent Absent Absent Absent NR-41 (sulfide-based UV Nitrogen gas 60 0.7 Present Absent Absent Absent NR-42 inorganic solid Atmospheric pressure Nitrogen gas 20 2.5 Present Absent Present Present electrolyte) plasma NR-43 Atmospheric pressure Nitrogen (98%)/ 20 4.1 Present Present Present Present plasma hydrogen (2%) gas R-5 AB No treatment — — 0.0 Absent Absent Absent Absent NR-51 (auxiliary UV Nitrogen gas 60 1.0 Present Absent Absent Absent NR-52 conductive EB Vacuum 20 0.2 Present Absent Absent Absent NR-53 agent) Atmospheric pressure Nitrogen gas 20 1.4 Present Absent Present Present plasma R-6 Natural No treatment — — 0.0 Absent Absent Absent Absent NR-61 graphite UV Nitrogen gas 60 1.5 Present Absent Absent Absent NR-62 (negative UV Nitrogen gas 240  2.4 Present Absent Absent Absent NR-63 electrode EB Vacuum 20 0.2 Present Absent Absent Absent NR-64 active material) Atmospheric pressure Nitrogen gas 20 2.4 Present Absent Present Present plasma NR-65 Atmospheric pressure Nitrogen (98%)/ 60 5.3 Present Present Present Present plasma hydrogen (2%) gas <Notes of Table> LCO: LiCoO₂ (lithium cobalt oxide) NCA: LiNi_(0.85)Co_(0.10)Al_(0.05)O₂ (lithium nickel cobalt aluminum oxide) LLZ: Li₇La₃Zr₂O₁₂ (lanthanum lithium zirconate, average particle diameter: 5.06 μm, manufactured by Toshiba Manufacturing Co., Ltd.) Li—P—S: Li—P—S-based glass synthesized above AB: Acetylene black (I): Region (I) 3,200 cm⁻¹ to 3,800 cm⁻¹ (II): Region (II) 2,000 cm⁻¹ to 2,280 cm⁻¹ (III): Region (III) 1,500 cm⁻¹ to 1,800 cm⁻¹ (IV): Reeion (IV) 1,020 cm⁻¹ to 1,250 cm⁻¹

EXAMPLES AND COMPARATIVE EXAMPLES

—Production of Electrode Sheet for All-Solid State Secondary Battery S-1—

180 zirconia beads having a diameter of 5 mm were injected into a 45 mL zirconia container (manufactured by Fritsch Japan Co., Ltd.), and the surface-reformed positive electrode active material (Particles NR-11) (8.0 g), non-surface-reformed LLZ (Particles R-3) (4.0 g) as an inorganic solid electrolyte, and propylene glycol monomethyl ether acetate (15 g) as a dispersion medium were injected thereinto. After that, the container was set in a planetary ball mill P-7 (trade name) manufactured by Fritsch Japan Co., Ltd., and the components were continuously mixed at a temperature of 25° C. and a rotation speed of 300 rpm for two hours, thereby preparing a solid electrolyte composition slurry for an all-solid state secondary battery.

The solid electrolyte composition slurry for an all-solid state secondary battery was applied onto a 20 μm-thick aluminum foil using an applicator (trade name: SA-201 Baker type applicator, manufactured by Tester Sangyo Co., Ltd.), heated at 80° C. for one hour, and then further heated at 120° C. for one hour, thereby drying the dispersion medium. After that, the electrode active material layer was heated (at 150° C.) and pressurized (600 MPa for 10 seconds) using a heat pressing machine, thereby obtaining an electrode sheet for an all-solid state secondary battery S-1 in which the thickness of an electrode active material layer was 150 am.

Electrode sheets for an all-solid state secondary battery S-2 to S-11 and HS-1 to HS-5 were obtained in the same manner. The amount of a negative electrode active material used was 8.0 g, the amount of a binder used was 1.0 g, and the amount of an auxiliary conductive agent used was 1 g. Meanwhile, S-2 to S-11 were electrode sheets for an all-solid state secondary battery satisfying the specifications of the present invention, and HS-1 to HS-5 were electrode sheets for an all-solid state secondary battery for comparison.

Meanwhile, in Table 2, an electrode sheet for an all-solid state secondary battery is expressed as “sheet”.

<Testing>

A bonding property test was carried out on the electrode sheets for an all-solid state secondary battery produced above. Hereinafter, a testing method will be described. In addition, the measurement results are summarized in Table 2 below.

<Bonding Property Test>

A 180° peeling strength test (JIS Z0237-2009) was carried out on the obtained electrode sheet for an all-solid state secondary battery.

Pressure-sensitive adhesive tape (having a width of 24 mm and a length of 300 mm) (trade name: CELLOTAPE CT-24, manufactured by Nichiban Co., Ltd.) was attached to the electrode active material layer of the electrode sheet for an all-solid state secondary battery. An end of the tape was gripped, the tape was folded 180° and peeled off 25 mm from the electrode active material layer, then, a single end of the electrode sheet for an all-solid state secondary battery from which the pressure-sensitive adhesive tape had been peeled off was fixed to a lower-side holding device installed in the following testing machine, and the pressure-sensitive adhesive tape was fixed to an upper-side holding device.

Testing was carried out at a load speed of 300 mm/min. After the initiation of the measurement, the pressure-sensitive adhesive tape was peeled off 25 mm, and then the pressure-sensitive adhesive force values measured every 0.05 mm in the 50 mm-long tape portions peeled off from the electrode active material layer were averaged, thereby obtaining a value of the peeling pressure-sensitive adhesive force (average peeling strength (N)).

The average peeling strength that is high at this time indicates a strong bonding force.

The peeling strength was measured by combining a standard-type digital force gauge ZTS-5N and a vertical electric measurement standard MX2 series (both are trade names, manufactured by Imada Co., Ltd.).

TABLE 2 Positive Negative Average electrode Inorganic electrode Auxiliary peeling active solid active conductive strength Sheet material electrolyte material agent Binder (N) Example 1 S-1 NR-11 R-3 — — — 0.91 Example 2 S-2 NR-21 R-4 — — PMMA 0.89 Example 3 S-3 NR-12 NR-31 — NR-5 PMMA 1.03 Example 4 S-4 NR-22 NR-41 — NR-51 PMMA 1.80 Example 5 S-5 NR-13 NR-42 — NR-52 PMMA-PMA 1.44 Example 6 S-6 NR-22 NR-43 — NR-53 PMMA-PHM 1.83 Example 7 S-7 — R-4 NR-61 — — 0.74 Example 8 S-8 — NR-42 NR-62 — PMMA 0.88 Example 9 S-9 — NR-43 NR-63 — PMMA 0.95 Example 10 S-10 — NR-43 NR-64 — PMMA-PMA 1.32 Example 11 S-11 — NR-43 NR-65 — PMMA-PHM 1.56 Comparative HS-1 R-1 R-3 — — — 0.12 Example 1 Comparative HS-2 R-2 R-4 — — PMMA 0.11 Example 2 Comparative HS-3 R-2 R-4 — R-5 PMMA-PMA 0.17 Example 3 Comparative HS-4 — R-4 R-6 R-5 PMMA-PMA 0.03 Example 4 Comparative HS-5 — R-4 R-6 R-5 PMMA-PMA 0.04 Example 5 <Notes of Table> PMMA: Polymethyl (meth)acrylate having a mass average molecular weight of 70,000, manufactured by Aldrich-Sigma, Co. LLC. PMMA-PMA: Poly(methyl methacrylate-methacrylic acid) copolymer having a mass average molecular weight of 70,000 and a molar ratio of 70:30 (prepared by a standard method of radical polymerization; the molar ratio indicates a monomer preparation ratio.) PMMA-PHM: Poly(methyl methacrylate-ethyl methacrylate phosphate) copolymer (trade name: PHOSMER M (manufactured by Uni-Chemical Co., Ltd.) having a mass average molecular weight of 70,000 and a molar ratio of 70:30

As is clear from Table 2, it is found that the electrode sheets for an all-solid state secondary battery containing the particles for an all-solid state secondary battery of the present invention in which the particle surfaces were reformed with a nitrogen element had a high peeling strength and an excellent bonding property.

From Table 2, it is clear that the all-solid state secondary battery of the present invention has a high peeling strength and an excellent bonding property.

The present invention has been described together with the embodiment; however, unless particularly specified, the present inventors do not intend to limit the present invention to any detailed portion of the description and consider that the present invention is supposed to be broadly interpreted within the concept and scope of the present invention described in the claims.

EXPLANATION OF REFERENCES

-   -   1: negative electrode collector     -   2: negative electrode active material layer     -   3: solid electrolyte layer     -   4: positive electrode active material layer     -   5: positive electrode collector     -   6: operation portion     -   10: all-solid state secondary battery 

What is claimed is:
 1. An all-solid state secondary battery comprising: inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, wherein a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more.
 2. The all-solid state secondary battery according to claim 1, further comprising: auxiliary conductive agent particles, wherein a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.
 3. The all-solid state secondary battery according to claim 1, wherein the proportion of the nitrogen element in the element composition of the particle surface is set to 0.1 atm % or more by an actinic ray.
 4. The all-solid state secondary battery according to claim 1, wherein the inorganic solid electrolyte particles are oxide-based or sulfide-based inorganic solid electrolyte particles.
 5. The all-solid state secondary battery according to claim 1, wherein the electrode active material particles are selected from the group consisting of electrode active material particles represented by any one of Formulae (B1) to (B5) and electrode active material particles belonging to (B6), Li_(a1)M¹O_(b1)  Formula (B1) Li_(c1)M² _(m1)O_(d1)  Formula (B2) Li_(e1)M³ _(m2)(PO₄)_(f1)  Formula (B3) Li_(g1)M⁴(PO₄)_(h1)X_(i1)  Formula (B4) Li_(j1)M⁵(SiO₄)_(k1)  Formula (B5) (B6) a carbonaceous material, tin, silicon, indium, and oxides and sulfides thereof in Formula (B1), M¹ represents a metal including at least one of Co, Ni, Fe, Mn, Cu, or V, a1 represents 0 to 1.2, and b1 represents 1 to 3, in Formula (B2), m1 represents an integer of 2 to 8, a plurality of M²'s each independently represents a metal including at least one of Co, Ni, Fe, Mn, Cu, Cr, or V, c1 represents 0 to 2, and d1 represents 3 to 8, in Formula (B3), M³ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, m2 represents an integer of 1 to 8, e1 represents 0.1 to 3, and f1 represents 1 to 5; and in a case in which a plurality of M³'s is present, the plurality of M³'s may be identical to or different from each other, in Formula (B4), M⁴ represents a metal including at least one of V, Ti, Cr, Mn, Fe, Co, Ni, or Cu, X represents a halogen atom, g1 represents 0.1 to 3, h1 represents 1 to 5, and i1 represents 0.1 to 5, and in Formula (B5), M⁵ represents a metal including at least one of Co, Fe, Mn, Ni, Cu, or V, j1 represents 0 to 3, and k1 represents 1 to
 5. 6. The all-solid state secondary battery according to claim 1, wherein the proportion of the nitrogen element in the element composition of the surface of at least one kind of the particles is 0.1 atm % or more, and one or more Raman spectral spectrum peaks are detected in at least one range of 3,200 cm⁻¹ to 3,800 cm⁻¹, 2,000 cm⁻¹ to 2,280 cm⁻¹, 1,500 cm⁻¹ to 1,800 cm⁻¹, or 1,020 cm⁻¹ to 1,250 cm⁻¹.
 7. The all-solid state secondary battery according to claim 1, further comprising: a binder.
 8. The all-solid state secondary battery according to claim 7, wherein the binder has an acidic group.
 9. A method for manufacturing the all-solid state secondary battery according to claim 1, comprising: a step of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by an actinic ray.
 10. The method for manufacturing the all-solid state secondary battery according to claim 9, wherein the actinic ray is plasma generated from a gas of any one of nitrogen, oxygen, hydrogen, carbon dioxide, ammonia, helium, and argon or a gas mixture of two or more thereof.
 11. The method for manufacturing the all-solid state secondary battery according to claim 10, wherein the plasma is low-temperature atmospheric pressure plasma.
 12. Particles for an all-solid state secondary battery which are electrode active material particles selected from the group consisting of inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table, auxiliary conductive agent particles or electrode active material particles represented by any one of Formulae (B1) to (B5), and electrode active material particles belonging to (B6), wherein a proportion of a nitrogen element in an element composition of particle surface is 0.1 atm % or more, Li_(a1)M¹O_(b1)  Formula (B1) Li_(c1)M² _(m1)O_(d1)  Formula (B2) Li_(e1)M³ _(m2)(PO₄)_(f1)  Formula (B3) Li_(g1)M⁴(PO₄)_(h1)X_(i1)  Formula (B4) Li_(j1)M⁵(SiO₄)_(k1)  Formula (B5) (B6) a carbonaceous material, tin, silicon, indium, and oxides and sulfides thereof in Formula (B1), M¹ represents a metal including at least one selected from the group consisting of Co, Ni, Fe, Mn, Cu, and V, a1 represents 0 to 1.2, and b1 represents 1 to 3, in Formula (B2), m1 represents an integer of 2 to 8, a plurality of M²'s each independently represents a metal including at least one selected from the group consisting of Co, Ni, Fe, Mn, Cu, Cr, and V, c1 represents 0 to 2, and d1 represents 3 to 8, in Formula (B3), M³ represents a metal including at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, m2 represents an integer of 1 to 8, e1 represents 0.1 to 3, and f1 represents 1 to 5; and in a case in which a plurality of M³'s is present, the plurality of M³'s may be identical to or different from each other, in Formula (B4), M⁴ represents a metal including at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, X represents a halogen atom, g1 represents 0.1 to 3, h1 represents 0.1 to 5, and i1 represents 0.1 to 5, and in Formula (B5), M⁵ represents a metal including at least one selected from the group consisting of Co, Fe, Mn, Ni, Cu, and V, j1 represents 0 to 3, and k1 represents 1 to
 5. 13. A method for manufacturing the particles for an all-solid state secondary battery according to claim 12, comprising: a step of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by an actinic ray.
 14. A solid electrolyte composition for an all-solid state secondary battery which is used for the all-solid state secondary battery according to claim 1, the solid electrolyte composition comprising: inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, wherein a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more.
 15. The solid electrolyte composition for an all-solid state secondary battery according to claim 14, further comprising: auxiliary conductive agent particles, wherein a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.
 16. A method for manufacturing the solid electrolyte composition for an all-solid state secondary battery according to claim 14, comprising: a step of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by an actinic ray.
 17. An electrode sheet for an all-solid state secondary battery which is used for the all-solid state secondary battery according to claim 1, the electrode sheet comprising: inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table; and electrode active material particles, wherein a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles or the electrode active material particles is 0.1 atm % or more.
 18. The electrode sheet for an all-solid state secondary battery according to claim 17, further comprising: auxiliary conductive agent particles, wherein a proportion of a nitrogen element in an element composition of a surface of at least one kind of the inorganic solid electrolyte particles, the electrode active material particles, or the auxiliary conductive agent particles is 0.1 atm % or more.
 19. A method for manufacturing the electrode sheet for an all-solid state secondary battery according to claim 17, comprising: Steps [1] and [2] below in this order, Step [1] of applying a solid electrolyte composition containing inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table and electrode active material particles; and Step [2] of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by irradiating the solid electrolyte composition with an actinic ray.
 20. A method for manufacturing the electrode sheet for an all-solid state secondary battery according to claim 18, comprising: Steps [1] and [2] below in this order, Step [1] of applying a solid electrolyte composition containing inorganic solid electrolyte particles having conductivity for ions of metals belonging to Group I or II of the periodic table, electrode active material particles, and auxiliary conductive agent particles; and Step [2] of setting the proportion of the nitrogen element in the element composition of the particle surface to 0.1 atm % or more by irradiating the solid electrolyte composition with an actinic ray. 